101 spinel twins: symmetry and beauty in silver

The universe is built on a plan the profound symmetry of which is somehow present in the inner structure of our intellect, Paul Valery, 19th century French Poet

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Silver, Kearsarge Mine, Houghton Co., Michigan. The specimen is 3.5 cm across. This native silver is a lustrous example of a “weave” of sliver crystals exhibiting spinel twinning. Photograph by Jeff Scovil. Click on any photo in the article to get a larger view.

When I first started building a mineral collection — back about 1960 — the single most compelling criteria for determining if a specimen was a “keeper” or just something for the beer flats filled with colorful, yet, unworthy rocks, was whether there was a euhedral crystal.  My fascination with the perfection of a sharp crystal face is not at all uncommon for beginning collectors.  The fact that nature could take time to construct something so perfect strikes a deep chord; the vast universe created by the ultimate act of violence – the big bang – and ruled by entropy, and inevitable decay, still values symmetry.  I recall an early discussion with my mother on the beauty of spring flowers – I asked her why she thought they were beautiful, and she responded with a joyful exposition on the bright and varied colors and the delicate nature of the pistil, and remarkable symmetry of the petals.  I told her that the petals were exactly like crystals since they are always alike, and must be following some sort of “rules”.

The English word symmetry comes from the Greek symmetria;  in turn, symmetria is a concatenation of  Greek words sun and metron, meaning “together” and “measure”. There is a substantial body of Greek literature that refers to symmetry as  “harmonious and beautiful proportion and balance”.  This philosophical definition of symmetry deviates from the strictly mathematical definition, but still projects the power of something that is predictable and has a geometric balance to be pleasing to the eye.  This “pleasing to the eye” is a euphemism for beauty — hard to define exactly, but beauty excites our aesthetic senses.

To me, there is nothing more pleasing to the eye than a silver specimen exhibiting spinel twinning – repeating patterns of crystals that produces a highly geometric weave.  The photograph at the top of the column is a silver from the Kearsarge Mine, Houghton Co., in the Upper Peninsula of Michigan. The specimen is defined by a central rib — an elongated stack of silver octahedrons, and branches intersecting the this rib at angles of approximately 60 degrees.  In turn, these branches have secondary branches exiting at similar angles.  The repeating geometry yields a specimen architecture that is clean and sharp – an exemplar of what the Greeks meant by symmetry.

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Silver, from a locality near Tongchong, Yunnan Province, China. Specimen height is 6cm. The wires are the result of decomposition of acanthite.  Jeff Scovil photograph.

Silver:  a special element

Silver is a remarkable element that can form an array of minerals; about 180 different species.  Thankfully, elemental silver is sufficiently inert to occur in nature and is widely distributed throughout the world.  Native silver is a metal of bright white color; it has the highest reflectivity of any metal.  Silver is also the best metallic conductor of heat and electricity and extremely malleable and ductile. These properties are, of course, a result of crystal and atomic structure, which is a face-centered cube with metallic bonds.  The atomic radius of silver is nearly identical to that of gold – and gold commonly substitutes into the silver crystal lattice.

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Native silver crystal forms, from Goldschmidt (1913). The octahedron is most common, although cubes are much coveted by collectors. The bottom 3 figures show spinel twinning.

Silver crystallizes in the isometric system, and although individual, sharp macro crystals are rare, the octahedron and cube forms are most common.  The largest individual crystals are from Kongsberg, Norway, where some octahedrons 3-5 cm on a side grace a few fortunate collections.

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Cubic silver in calcite; Kongsberg, Norway.Each of the large cubes are approximately 1 cm on a side.  Jeff Scovil photograph.

As a rule, crystals of silver are equi-dimensional or platy. The platy nature comes from the propensity from silver to twin (this is similarly seen in gold and copper) on octahedral faces {111}.  This twinning is known as spinel twinning and is described below.  The conditions for when spinel twinning occurs appears limited – although silver masses of spinel twins are known from hundreds of locations, there are only three or four localities where this type of silver crystallization is common.  The two most famous localities are Batopilas, Mexico and Chanarcillo, Chile.

By far, the most common form of silver in a mineral collections is the wire – which is a secondary growth from the decomposition of silver sulfides and sulfosalts. Any silver deposit that undergoes supergene enrichment inevitably has silver wire specimens.  The picture at the top of this section of the article is a fine silver wire mass from Tongchong in China.  The wires in this specimen are attached to a very small piece of acanthite, no doubt the host material that provided the silver.  All silver sulfides and most silver sulfosalts will produce silver wire upon disassociation — especially promoted by heating.  Although wires can be extremely interesting and coveted specimens for collectors, there are been numerous cases where the wires were “grown” by unscrupulous collector/dealers and passed off as “natural” specimens.

Beauty in Nature

When I hear the word “beautiful” used to describe minerals by collectors I often ask what they mean.  More often than not, the answers seem wanting to me.  Mostly, it is about color — pink and red minerals are always “beautiful”, but black and brown minerals are “interesting”.  Although color can transfix, and certainly evoke emotion, I can not relate to it as the primary metric of natural beauty.  I am also looking for structure in my surroundings – a window into the soul of nature, order out of the chaos all around me.

A seminal event for me was attending “math summer camp” during the summer between 7th and 8th grade.  The instructor was an outstanding teacher named Jack Gehre, and his focus was geometry and trigonometry. Early in the class Mr. Gehre introduced Euler’s formula; for any normal polyhedron, the sum of the number of faces plus the number of vertices, minus the number of edges always equals 2.  I spent the rest of the summer camp trying to understand why.  I suddenly had a “rule” in nature that I could apply to my mineral collection — a rule mysterious and powerful, but incredibly simple.  It was beautiful.  I did not know much about Euler then, but later in college I was introduced to another “law” by Leonhard Euler — an incredible 18th century Swiss mathematician — that has to be the most beautiful equation in all of nature.  I was in a class on series analysis, and the professor, Alan Sharples, walked in the first day of the semester and wrote the following on the black board:

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Sharples said, “this is Euler’s identity, a remarkable assertion.  Prove it.  That is all for this first day of class.”  Turns out that this is pretty easy to prove, but when I viewed this on the blackboard I was transfixed — it was pure beauty.  Imagine three essential mathematical constants – e, pi, and  – combined to equal -1.  Wow – simple, brief, and exact.  To this day I view this as a definition of beauty (Euler’s identity is routinely identified as the one of the most beautiful equations in science).

Euler’s identify may seem a long ways from realm of beauty in the mineral kingdom.  However, to me, they are very much related.  Simple, surprising, and an expression of natural symmetry.

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Herringbone silver mass, Batopilas, Chihuahua, Mexico. The Specimen is 3.75 cm across. Jeff Scovil, photograph.

Respect the Spinel Twin

Crystal growth in nature is quite complex; the crystal form, crystal size, crystal chemistry all are expressions of the paragenesis. Crystallization for most geologic materials involves the precipitation of a solid (the crystal) out of a solution or solvent (usually hot thermal fluids, although solutions of nearly any temperature can carry dissolved loads of ions and cations).  Crystals start with nucleation of a few molecules from the solution, and then growth occurs by pulling the necessary ionic components out of solution.  The rate at which individual crystals grows depends strongly on the saturation level of the ions of interest – supersaturated solutions appear to be able to grow crystals at extraordinary rates (at least compared to geologic time!), sometimes at several cubic cm per hour.

It is not clear who first recognized twinning in crystals, but it was first written about in detail by Rene-Just Haüy in his epic tome Traité de Minéralogie, published in 1801. In the beginning part of the 20th century there were a number of studies to understanding twinning in minerals. The classic definition was introduced by Friedel in 1926: A twin is a complex crystalline edifice built up of two or more homogeneous portions of the same crystal species in contact (juxtaposition) and orientated with respect to each other according to well-defined laws. The “well-defined laws” all are based on some simple ideas, the most important of which is that within a crystal core that a least one lattice row (i.e., a crystal edge) is common to two different crystals. The figures below illustrate this concept — the lattice of a cubic crystal is defined by four points, and a plane can be drawn through these points that allows a second crystal to share lattice points but have a rotated orientation. Twinning adds symmetry to a crystal aggregate, most commonly about a rotation axis or reflection across a plane. In the metals copper, gold and silver, a particular type of twin is common, called the spinel twin.

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Spinel twins are so-named because it is a very common habit seen in the mineral spinel. They are contact twins, meaning that have a planar composition surface shared by two individual crystals; this surface is along an octahedral face (written as {111}), and means that there is a rotation of 180o about the contact plane. This is illustrated by the lower figure above – there are two octahedrons joined along a contact plane, but the top terminations “point” in directions and are separated by 120o. The figure below shows how spinel twins can be flattened, and give the characteristic triangular faces that are seen on platy crystals of silver (and gold).

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Notional relationship between an octahedron and a spinel twin producing a triangular type crystal face. This is “notional” in that this is NOT how the spinel twin evolves with time, but rather, a visual guide to compare an octahedron (left) and triangular face (right).

In silver, spinel twinning almost always repeats itself with regularity, producing a pattern that resembles a weave of wires.  The silver at the top of this section of the article is from Batopilas, Chihuahua, Mexico, and is an example of a mass of spinel twins.  Through the middle of the specimen is a series of parallel elongated crystals, and growing “off” these strands are regular strands oriented at 60 degrees (or 120 degrees, strictly speaking). These are all spinel twins – repeating some natural frequency that is due to a long lost geologic condition.  Once assembled, the spinel twins from an aggregate of crystals that has been called a “herringbone” silver in reference to the similarity to the shape of the rib cage of the smelly game fish beloved by the peoples of the Baltic.

Why do spinel twins form in silver?  Under certain ideal conditions, a single large crystal represents a “minimum” energy condition, and thus is due to an important thermodynamic rule — a chemical system will stabilize at state of least energy.  If individual crystals are a minimum energy state, then twinned crystals are by necessity at state of higher energy, and thus should be rare. However, environmental conditions tend to localize energy states; for a supersaturated solution, the crystal growth is extremely rapid, and twinned crystal allow more ions to join a crystallize aggregate faster, thus minimizing a local energy state.  For all “herringbone” silver specimens it appears that the conditions of formation require a supersaturated solution, low in concentrations of sulfur, and extremely rapid crystal growth.  These conditions are relatively rare in most epithermal vein deposits; it is very uncommon to find a spinel twinned silver specimen from the great silver deposits of Colorado, Ontario or Freiberg!

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Large silver plate (7.5 cm from side-to-side) from Chanarcillo, Chile. The specimen is a weave of spinel twins – and is my favorite silver specimen in my collection. Jeff Scovil photograph.

The silver pictured above is my favorite native silver in my entire mineral collection.  This is a large “herringbone” plate with a three dimensional repeating pattern of twins.  The specimen represents something remarkable in turns of crystal growth.  The tiniest variations in chemistry or temperature during growth would have truncated the growth of this silver weave.

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Close up of the Chanarcillo specimen shown above. The central rib is an elongated chain of octahedrons. Field of view is 3 cm. Repeatedly, silver crystal “twin” off the octahedral face(s). At the very top of the specimen there are identifiable octahedrons.

A close examination of the Chanarcillo herringbone yields views of spectacular detail – endlessly repeating, and shouting the fundamental rules for symmetry in crystals. Along the edges of the crystalline mass you can see individual octahedrons – the termination of various elongated crystals.

Beauty and the pretenders

Rapid growth in silver often produces crystalline masses that are complex.  However, spinel twins are distinct, and uncommon.  Rapid growth often leads to dendritic masses – mostly silver feather patterns or strings of stacked cubes. These dendrites are not spinel twins; in fact, instead of fundamental order, they represent chaotic growth.  Although there is some sense of beauty in the randomness of dendrites, it is mostly through “self-similarity” – various patterns that appear to scale with size.  This is fundamentally different than ordered spinel twins – and in many ways points to disordered processes.  I am always shocked (okay, probably an overly harsh expression of emotion) when I find dealers selling “herringbone” silvers that are in fact dendrites.  That is like marketing hamburger as Filet Mignon.  Similarly, silver wires can certainly be attractive; however, they are products of mineral destruction not construction.  To me, beauty in silver spinel twins is about construction, order, and symmetry.  Defining beauty will allows be in the eye of the beholder — it is just better when there are rules involved.

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The Glue Does Not Show: Mineral restoration and specimen value

Shades of grey wherever I go
The more I find out the less that I know
Black and white is how it should be
But shades of grey are the colors I see

Billy Joel, Shades of Grey, released 1993.

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Stephanite, Husky Mine, Mayo Mining District, Yukon Territory, Canada. The crystal group is approximately 6.3 cm across, and outstanding for the locality; Husky Mine polybasite and stephanites typically have an iridescence that it probably caused by light reflection/refraction in a very thin coating of an unknown silicate. Jeff Scovil Photo.

In the mid 1980s I was first asked to be a judge of the competitive mineral exhibits at the Tucson Gem and Mineral Show. At that time the TGMS competition, and its two top awards – the McDole Trophy (best case of minerals entered into competition) and the Lidstrom Trophy (best individual mineral entered into competition) – were considered the pinnacle of the mineral world. The winners of these awards looked like a “Who’s Who” of the mineral collecting community, and every year the competition was passionate and savage. The rules for the McDole and Lidstrom awards were few; it was based on the judges experiences, biases, and an element of luck on who decided to enter the competition. The judging for the McDole and Lidstrom awards was also a “discussion” rather than some type of formal poll — a judge with a domineering personality could filibuster the other judges into accepting his or her opinion.  I recall clearly the discussion around a particular specimen entered into the Lidstrom competition that I was fond of;  “We can’t possibly consider that specimen a best – it has been repaired!”  The pronouncement carried such an air of academic certitude that I immediately agreed.  Of course, it had been repaired!  How could it really be a great mineral specimen if there was some glue involved!

It was not too long after that I began to ponder the absurdity of dismissing anything that is repaired as inherently flawed (on a personal note, now that I have multiple metal parts in various joints, I embrace the repaired).  Repairing a mineral is rather common – mineral extraction is inherently a violent activity, and the very act of handling a specimen introduces the possibility of drops, dings and scratches. But there is still a feeling that repairs should affect the monetary value of a specimen. I don’t think I have ever been to mineral show where I have not heard some version of the conversation between a dealer and a collector where the potential purchaser doesn’t ask for a significant discount because the specimen has been repaired.  The stephanite pictured at the top of this article is a fantastic complex crystal from the Husky Mine in the Yukon Territory, Canada.  I first committed to buying this piece for my collection around the year 2000.  However, when I went to go pick it up from the dealer I opened the box and the marvelous sample of “brittle silver” was in three pieces!  The stress of transport had caused the crystal to part along inter-growth boundaries.  I was heart broken, and walked away from a masterpiece.  The dealer repaired the piece expertly, and eventually I was able to acquire it.  However, several years later I was transporting it to be photographed and it “parted” again!  Fortunately, it was once again restored, and now sits permanently in my mineral cabinet never to travel again.  I believe it is the best, or one of the best, Husky Mine stephanites in existence, and the fact that it has some clear cyanoacrylate helping to hold it together is inconsequential.

Repair would, thus, seem to be a rather “black and white” issue – restoring a collectable to its original configuration is not fraud or even misrepresentation of nature. Sadly, it is not “black and white”, and repair/restoration has become a spectrum disorder in the mineral collecting world.  Today many consider filling missing gaps in crystals with acrylic resin, buffing away scratches on crystal faces or even heating a specimen to “restore” its primordial color as simply “sophisticated repair”.  Not black and white, but shades of grey.

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The Pieta, carved by Michelangelo in the 16th century. The statue has been repaired a number of times in the last 500 years — most recently removing the damage done by a geology hammer (!) wielded by a lunatic.

Real Repairs

The Pieta is a signature masterwork of Italian sculptor Michelangelo, and one of the most famous works of art in history. Michelangelo was only 23 years old when he carved the single block of Carrara marble into a haunting image of a crucified Jesus being held by his mother. By any figure of merit, the Pieta is priceless. Yet, it is repaired – several times! The four fingers of Mary’s left hand were snapped off during a move in the 18th century (restored in 1736).  The most egregious damage occurred in an instant of insanity when Laszio Toth, an unemployed Hungarian geologist attacked. Toth struck the Pieta more than a dozen times with his field hammer, breaking off Mary’s arm, part of her nose, and chipping her face.

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Mary’s hand after the Toth attack. More than a hundred fragments of marble had to be reassembled to restore the Pieta.

The repair of the statue was done by a team of 10 people painstakingly reassembling the fragments and filling in voids with a mixture of powdered marble and polyester resin.  When the restore work was unveiled it was claimed that it was impossible to identify where the damage had been.  Some experts suggest that with the passage of time the resin has perceptibly changed color, but in general the repair has faded into history and the magnificence of the Pieta has been restored.

The restoration of the Pieta might be a fanciful stretch as an analogy for mineral repair, but it does frame the philosophy of specimen “value”.  It is highly unlikely that the reconstruction of Mary’s left hand would effect the value of the Pieta if the Vatican decided to part with the treasure;  I can’t imagine any art collector asking the Vatican for a “discount” because the marble was not exactly as Michelangelo carved it long ago.  On the other hand, the restoration process went to great lengths to assure that nothing changed from the original – no added expression to Mary’s face, no extra lamb seated at her feet.

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The Alma Queen; a 10 cm, complex rhomb of rhodochrosite perched in a matrix of fine quartz crystals.  This “rock” was found in 1966 at the Sweet Home MIne, and has been called the finest mineral specimen in the world.

The Rhodochrosite Royalty – a family full of plastic surgery

In 1966, a 90 year old silver mine located on the slopes of Mt Bross – one of Colorado’s 53 peaks that have elevations in excess of 14,000 feet above sea level – yielded a remarkable mineral specimen.  The mine was called the Sweet Home, and during its on-again, off-again mining history had periodically produced some of the world’s best rhodochrosite.  However, the standard for rhodochrosite was reset when a mining crew drilled into a pocket and found a 10 cm rhombohedron of cherry red rhodochrosite perched on a slab of pencil thin white quartz. The specimen was purchased by one of Colorado’s earliest fine mineral dealerships, Crystal Gallery, for the princely sum of $2500.  Crystal Gallery was a partnership between Merle Reid and Colorado collector legend George Robertson.  The rhodochrosite ended up in the hands of Peter Bancroft (much to the chagrin of George Robertson), who christen the piece as the “Alma Queen”, in recognition of the mining town a few miles southeast of the Sweet Home Mine (the picture above is “official” photo of the Alma Queen from its present home, the Houston Museum of Natural Science).  In short order the Queen passed through a hands of a number of famous mineral dealers, finally becoming a prized possession of Perkins Sams.  In 1986, Sams sold the Queen to Houston Museum – and a few years later it was being moved and was broken!  Actually, it was not too surprising given that the rhodochrosite has perfect cleavage, and the huge crystal was isolated and perched on matrix.  Fortunately, the crystal was “repaired” – it is impossible to see the glue reattaching the rhomb – and is still considered a masterpiece.

The Alma Queen enticed others to want to return to the Sweet Home Mine and search for more rhodochrosite. In 1991 Bryan Lees and partners began a professional and systematic exploration for mineral specimens.  In 1992 Lees’ operation discovered a 1.5 meter long pocket that yielded incredible — larger than even the Alma Queen — specimens.  Most of the crystals were detached from matrix, jarred from their natural perches by the mining activity.  The largest of the crystals was more than 15 cm across, and was dubbed the Alma King.

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Bryan Lees holding the Alma King, just outside the Rainbow Pocket.  The crystal was some 15 cm across!

The Alma King was eventually reattached to matrix, and was brought to the Tucson Gem and Mineral Show in 1993.  I remember seeing the specimen, and was stunned.  I also recall standing next to a old time collector who remarked “too bad it is repaired”.  Wow – my thoughts were not conflicted at all – the repair was sincere and returned a natural masterpiece to it’s rightful magnificence.  It was exactly like the restoration of the Pieta!

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The Alma King – repaired. The specimen now sits in the Denver Museum of Natural History.

There is little argument that the repair of the Sweet Home rhodochrosites was the right course of action, and certainly did not diminish the value of the specimens.  However, it also coincided with the crest of a darker tsunami in the collecting hobby that demanded specimen perfection, and art aesthetics overtaking  all other metrics of mineral specimen evaluation.  A significant percentage of the Sweet Home specimens required repair, although the evolving euphemism was “specimen preparation”; a dialog developed around the theme of “returning the specimen to the condition it was in nature”.  This catch phrase has become the a divide between collectors;  those that prize the art of mineral specimens are willing to see flaws removed by polish and resins, while other collectors recoil at any man-induced enhancements and celebrate only that which can be documented “as found”.  This gulf is wide, and brings cries of “fake and fraud” from collectors in the later group when they view many of the world’s best mineral specimens. However, this group of collectors – the old school – is dying away.  Not yet irrelevant, but mostly marginalized.  I am old school.

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The cover of the Mineralogical Record, January 2015. On the cover is one of the most amazing tourmaline specimens in existence, and the volume is full of information on the Pederneira mine. What is missing is the painstaking history of specimen repair and restoration – much work is done with added materials.

When a grey line becomes red — and crossed

In the last 50 years the mineral collecting hobby has seen dramatic changes – or perhaps evolution.  What was once the realm of rockhounds is now a glided age of art.  One of the most obvious symptoms of this change is what collectors accept and expect in a mineral specimen.  Repair and restoration have always been important for mineral specimens; however, the definition of repair and restore has changed as prices have escalated.  There has always been a desire to make specimens attractive, but today it is expected that many  specimens are oiled, waxed or sprayed with silicon to enhance their luster and hide their imperfections.  Use of these cosmetic trappings was once a “red line” for collectors – absolutely rejected.  But just like US foreign policy on the use of chemical weapons, that red line was faded to grey.  A tour through the many hotel rooms of the “high end” mineral dealers participating in the 2015 Westward Look Fine Mineral Show in Tucson (February 6-8) reinforces this dramatic shift;  it is fair to say that most expensive fluorite specimens for sale have been treated with oil, every recent amazonite dug from the pegmatites in the high peaks of Colorado has been “juiced” to enhance the luster, and most gem-quality garnets are getting at least a spray of enhancement.  And, further, casual conversation with collectors seems to reinforce that this is what they want.  Perfection is essential for a work of art.

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A comparison of “before and after” for a cut emerald. The cut stone on the left is natural, and on the right has been treated with cedar oil (from http://www.jfjco.com/2014/05/18/emerald-treatments/)

The desire to “improve” minerals is a couple of thousand years old.  There is written accounts of Greeks using cedar oil on emeralds to enhance the color.  The purpose of the oil was to fill the flaws and cracks with a material (the oil) such that when light is shined on the crystal there would not be reflections from the imperfections.  The cedar oil had approximately the right index of refraction (about the same as the emerald itself), and low enough viscosity (when heated) to flow into the tiny cracks, but high enough such that it would remain (at least for a while) after treatment.  Today the oil is mixed with a polymer which “fixes” the oil.  There are about a half dozen “restoration” labs in the US that work on minerals, and most have proprietary processes to do essentially the same thing as the cedar oil treatment except for fluorite, sphalerite, garnet, etc.  The science behind these processes is fairly sophisticated — but the treatment is rarely disclosed.

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Classic Gary Larson cartoon – Rowing in Circles. This reminds me of specimen restoration – dealers on one side, collectors on the other. Dealers provide what collectors want, and collectors hear from dealers what specimen perfection should be. It is just rowing in circles.

Today it is hard to “lay blame” for the practice of mineral restoration that relies on removing perceived imperfections at the doorstep of dealers.  The nature of the “trophy collector” is to find perfection – and that sense of perfection does not have to be the hand that nature dealt.  Further, it is clear that repair and restoration no longer decrease specimen value, but actually increase value.  As Sir Walter Scott opined: Oh what a tangled web we weave, When first we practice to deceive.

Old School with a New World Order

I love collecting minerals – it is something that I have done with passion for more than 50 years.  I have changed along the way, and the hobby has changed even more than I.  I am deeply disturbed by many of the changes, but that does not make them “wrong”. Just as I am aghast at at what I perceive as the personal values of generations other than mine, my sense of why I collect, and what a mineral specimen means to me, does not have to be shared with others.  The Dalai Lama says: “Happiness is not something ready made. It comes from your own actions.”  I don’t need to change what and how I collect.  It is the science and human story that are codified and crystallized in my minerals. That is why I happily collect that which is repaired and total reject oils and waxes.  A red line.

Tales from the Tags: Mineral Labels and Specimen Value

I go down to Speaker’s Corner I’m thunderstruck They got free speech, tourists, police in trucks Two men say they’re Jesus one of them must be wrong – Dire Straits, 1982 song Industrial Disease

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Chalcopyrite coating acanthite Joachimstal, Bohemia (now in the Czech Republic).  Originally in the A.F. Holden Collection, bequeathed to the Harvard Mineral Museum, traded out and sold to William Pinch, and eventually came to my collection from dealer Cal Graeber.

One of the questions I get asked most often when I visit a mineral show: “Is it real?”.  I mean this in a mineralogical sense, not a judgement of my personality.  The origin of the question is uncertainty about a mineral sample, and the particular inquiry is focused on whether the mineral is as advertised, or “fake”.  The nature of fakery in the mineral hobby can be subdivided into four broad categories:  (1) is the mineral actually identified correctly, (2)  has the mineral specimen been enhanced, repaired or constructed, (3) is the mineral actually natural, and (4) is the ancillary information with the specimen – locality information, previous ownership, etc. – correct?  To me, the last category is particularly vexing.  The ancillary information, usually provided in a label or series of labels associated with a specimen, documents the history and significance of the specimen. I collect minerals partially because of the their “science” (chemistry, geology, and crystal beauty), but also because they are artifacts of history.  Someone had to mine the specimen, decide it was worth keeping, pass it on to a collector or dealer that valued it, and finally making its way to my collection.  From underground mine to my collection the specimen develops a patina of human history.  I very much value this history —  the story in the label with the mineral is part of its “worth”. The specimen pictured above is an exemplar of a mineral as a historical artifact.  The specimen is a miniature sized matrix acanthite with an epitaxial coating of chalcopyrite. The locality is Joachimsthal, one of the most important historic silver mining regions in the world.  The specimen has a well documented pedigree:  it was in the A.F. Holden collection that was bequeathed to the Harvard Mineral Museum in 1913, and transformed Harvard’s collection from a typical university cabinet into one of the world’s greatest mineral holdings.

Chalco.acanthite

Labels for the chalcopyrite coating acanthite specimen pictured at the top of the article. The specimen was in the A.F. Holden collection, went to Harvard, traded to a dealer that sold it William Pinch. Eventually, Pinch sold the piece and it made its way to my collection in the 1990s.

In 1912 the Engineering and Mining Journal declared that the finest collection of minerals in the United States is “believed to be that in the American Musuem of Natural History in New York, the basis of which was the famous Bement collection. There are several important private collections. Among those, that of Col. W.A. Roebling, Trenton, N.J., is considered to be the best; anyway, the largest. Next in rank are probably the collections of A.F. Holden, Cleveland, Ohio and Fred Canfield, Dover, N.J.” Albert F. Holden graduated from Harvard in 1888 with a degree in Mining Engineering. After graduation, Holden entered the family mining business, and by 1906 he had built one of the largest mining and refining companies in the world. His holdings included what would become the Bingham Canyon copper mine in Utah, and dozens of mines spanning the mineral wealth of Alaska to Mexico.  In the 1912-13 Annual Report on Harvard University, the curator of the Mineral Museum, John Wolff, wrote “received this year a mineral collection which represents the greatest single gift of minerals made during its history of one hundred and twenty years…Mr. Holden had found time in the last eighteen years to accumulate one of the finest private collections in existence….As a result, the larger part of the six thousand specimens are of the highest quality, while many are unique.” In the detailed instructions to Harvard accompanying the collection, Holden wrote “There shall be no obligation on the Museum authorities to keep any of the specimens when they have lost their scientific interest”. Although the chalcopyrite coating acanthite in my collection is modest, its tie to a mining great, and subsequent membership in the Harvard Museum, and ultimately its pathway into one of the great modern collectors, Bill Pinch, is what makes it “more” than a pretty mineral.  Remove the labels, and the specimen is interesting, but it loses its significance.  The tale told of specimens from labels is their character — and it is also why labels can also be used to deceive or misrepresent.

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Acanthite mounted on a wood pedestal from Bryn Mawr.

The original mineral twitter:  Mineral Labels

I am often surprised that many mineral collectors don’t spend much intellectual capital on the pedigree of the specimens that they pursue and collect.  That statement is, of course, a gross generalization because there are many collectors that intensely focus on the specimen history, but most collectors are first and foremost interested in the perfection of the specimen itself.  However, every specimen has a story to tell, and often that story is gleaned from a few lines written on an old mineral label.  Although labels may only contain the briefest inscriptions, these are often delightful clues to the thoughts and passions of the original collector. The picture above is a large thumbnail of acanthite from the Las Chispas Mine, Arizpe, Mexico.  For a very brief period, the first decade of the 20th century, the Las Chispas mine near Arizpe in Sonora produced some of Mexico’s largest and best specimens of polybasite crystals, large clusters of “poker chip” stephanite crystals, fine acanthite crystal clusters and a few very fine pyrargyrite specimens. Many of the specimens were saved through the enlightened efforts of mine manager Edward L. Dufourcq (1870-1919), and now populate museums and privates collections worldwide.  The pictured specimen is fairly unremarkable, even if distinctive of Las Chispas acanthites.  However, the label (and the wood stand that holds that displays the specimen) are what make this a historical artifact.  I purchased this specimen from a dealer in 1986 – but what I saw when it was displayed in his stock was the label — it is a very distinctive “Vaux” tag! George Vaux (1863-1927) was an attorney and member of one of the most important Pennsylvanian families – in fact, he was the 9th George Vaux (and passed the name on to his son too!). George Vaux was the nephew of William S. Vaux, who one of the earliest American mineral collectors. George followed his uncle’s lead and passionately collected minerals. When he died in 1927 he had amassed an amazing collection, particularly rich in South American and Mexican specimens (Vaux’s Chanarcillo proustites are still considered some of the finest examples of what I believe is the most beautiful mineral). Vaux lived in Bryn Mawr, located west of Philadelphia, and upon his death his family kept the collection intact and on display in their home. Bryn Mawr is home to the small college of the same name, founded by the Religious Society of Friends (Quakers) in 1885. In 1958 the family decided to donate his collection of more than 8,000 specimens to the college – and suddenly a small women’s liberal arts college had a major mineral holding! The transfer of the collection included Vaux’s labels – there are several types, but several thousand were the simple lined cards, with handwritten descriptions (like the one pictured above). In the early 1980s many of the Vaux specimens were traded out of the Bryn Mawr collection, including my acanthite.  The wood stand and black wax mount were Vaux’s work.  On the base of the stand Vaux wrote “Cahn, 11/20” which indicated that he had bought the specimen from Lazard Cahn, a Colorado Spring mineral dealer.  Eventually, it was acquired by Al McGinnis (a San Mateo dealer) for his private collection, which was dispersed upon his death. A few years after I acquired the Arizpe acanthite, I found another Vaux labeled acanthite specimen in the stock of mineral dealer Gene Schlepp.  In fact, the Vaux label was was tagged with the number 703, only a few digits different than the Arizpe piece!

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Aguilarite, Guanajuato, Mexico.

The Vaux label stated that the specimen was Argentite (acanthite) from Guanajuato, but I suspected the specimen was actually Aguilarite (Ag4SeS), a far rarer mineral.  The skeletal dodecahedrons are distinctive of the species, and the specimen looked very much like the very best aguilarites I had seen in other collections.  I purchased the piece, and hurried off to the lab to do an x-ray.  My hopes were confirmed – a outstanding aguilarite with history to boot!

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Vaux label

The front of the Vaux labels only tells part of the story.  Turn over a Vaux label and there is a few scribbles that connect Vaux to his mineral suppliers.  Below is a picture of the Arizpe and Guanajuato labels.  In Vaux’s hand writing you can see where and when he acquired the specimens.  The Aguilarite was obtained from Wards in 1895 — which is very consistent with the very best samples were mined.  Around 1890, Ponciano Aguilar, superintendent of the San Carlos mine at Guanajato collected an “unknown” that he thought might be Naumannite, and sent it to S.L Penfield for identification — and Penfield discovered it was a new mineral and named it in honor of Aguilar.

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Back of the Vaux labels; where the specimen was purchased, when it was purchased, and a three letter code. The code is likely the purchase price.

A mystery on the Vaux labels are the three letters scribbled after the date of purchase.  I have looked at about a dozen Vaux labels and they always have these initials, all different.  Wendell Wilson, editor of the Mineralogical Record, suggested that this might actually be an encrypted purchase price.  Several collectors from the first half of the 20th century used ciphers to record value.  Martin Ehrmann used “tourmaline” as his  cipher — 10, non-repeating letters, each corresponding to a numeral, 1-9 and 0 (e.g.  tne would translate to 190).  Carl Bosch, whose fabulous collection ended up in the Smithsonian Institution, used a similar code, with amblygonit thought to be the cipher used to record value in German Marks.  I don’t have access to nearly enough of the Vaux labels to “break the code”, but it is likely that the three letters are some important secret about the specimens. Not all minerals come with a rich history, and when there is a documented pedigree it is still hard to convert that history to a monetary value.  The Vaux labeled specimens in my collection are cherished by me, but in the future (hopefully distant future) when they are sold to other collectors the value will be mostly determined by comparison of the specimens with “their peers”.  The aguilarite will still be one of the best in the world, with or without the label.  But the real value will be the story behind the minerals – it may not be monetary value, but it will be fingerprints of humanity on stones recovered from the Earth.

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Bideauxite, Tiger, Arizona

When Labels Go Bad

One of specimens I treasure the most in my collection is a Bideauxite, a very rare lead-silver chloride (Pb2AgCl3(F, OH)2) from Mammoth-St. Anthony Mine, Tiger, Arizona.  The photograph above is a closeup of my specimen, and displays two hexoctahedral crystals of Bideauxite associated with boleite on a quartz matrix — the crystals are tiny, only a few mm across.  The unusual chemistry of Bideauxite requires a very restrictive set of conditions for formation, and in fact, the mineral is only documented to come from two localities:  Tiger and a small prospect in  Tarapaca, Iquique Province, in northern Chile.  The species is named after the late Richard Bideaux, a good friend and a fountain of knowledge for all things mineralogy (he is co-author of the Handbook of Mineralogy), especially Arizona mineralogy (co-author of Mineralogy of Arizona).  Richard “discovered” the mineral when working on his thesis at Harvard;  he was going through material in the Harvard Mineral Museum from Tiger and found a tiny gray-pink fragments of a mineral he thought was chlorargyrite on boleite.  Richard sent the material to Sid Williams who determined that it was a new mineral, and named it Bideauxite. In 2005, Dave Bunk bought part of the mineral collection that contained many specimens from Erberto Tealdi (the late editor of Rivista Mineralogica Italiana) collection. Tealdi collected a large suite of minerals from Colorado — and in the  material Dave acquired was the most amazingly labeled sample:  Bideauxite, Sherman Tunnel, Leadville, Colorado.  Acquired, Rich Kosnar.  Looking at the sample I immediately knew that it likely Bideauxite, but what a bizarre reference to the Sherman Tunnel!  Never has there been a more ridiculous assertion for a locality — wrong geology, wrong mineralogy, and about as believable as the theory that Roman Christians established a colony on the outskirts of Tucson, Arizona around 700 AD (this theory is based on an archeology hoax, but will live forever on the internet – I love archeological hoaxes!). It is clear that the original label listing the Leadville locality was used to deceive, but really it was a rather flaccid attempt. I eventually obtained the Bideauxite from Dave Bunk, and have labeled it as from “Tiger.” This is an example of a very troubling phenomena in which the Label is Bad.  In the case of the Bideauxite, the bad label has little consequence because  it was so preposterous.  However, for the very reason that labels add to the value of specimens — both in terms of history and monetary value — the issue of bad labels is one of the worst diseases in the mineral collecting hobby.

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The Colorado Dragon

Recently, Pala Minerals published an article about the sale of arguably the most important Colorado mineral specimen — a gold sample from the early days of the Colorado’s rich mining history — in their internet newsletter (http://www.palaminerals.com/news_2014_v2.php). The specimen is fabulous – more than 5 ounces of crystallized gold that demands attention.  The specimen is reputed to be from the Gregory Lode, Gregory Gulch, Gilpin County, Colorado – the label is shown below.  The significance of the label is “Gregory” — as in John H. Gregory.  Gregory, a prospector from Georgia, is credited with discovering the first major Colorado gold deposit located near what would become Central City, in May, 1859.  Gregory sold his claims, and pretty much disappeared  (although there are many Gregory legends, mostly they are unsubstantiated canard).  The label changes the “Colorado Dragon” from a great mineral specimen and transforms it to a hugely signifiant historical artifact.  Further, the mineral label states that the gold actually belonged to John Gregory, and that he had personally donated the treasure.  There is absolutely no other evidence that Gregory collected or owned this outstanding gold, nor that he donated specimens, but the label titillates!

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Label included with the Colorado Dragon.  Note that it states Gregory donated this gold, even though he disappeared in the early 1860s.

The “original label” for the Colorado Dragon is stated to be from the State Historical Society. The State Historical Society received minerals originally acquired by the Colorado Bureau of Mines over a period of about 80 years, in 1956.  This mineral collection was filled with history – it had specimens from senators, miners, and millionaires.  The label above serves as exculpatory evidence for those that would cast doubt on the provenance of the gold.  The faded piece of paper with a few typed phrases links the nugget with the birth of the Centennial State.

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A label accompanying the Colorado Dragon, from the Colorado School of Mines

Eventually, the Historical Society gave the mineral specimens to the Colorado School of Mines, and it was placed into the Mineral Museum holdings.  The photo of the label above is stated to be the School of Mines tag associated with the specimen.  In 1990s the Colorado Dragon was obtained by Colorado Dealer Richard Kosnar (the same Kosnar associated with my bideauxite) from the School of Mines.  This year the specimen was obtained by George Hickox a noted Colorado gold collector. This would be a remarkable tale, but just as the labels add immeasurable value to the gold, they also cast a dark cloud over the authenticity of the specimen.  The problem is that there are at least two more specimens labeled “number 5600” – so three competitors to the throne!  Two of the specimens are labels EXACTLY the same (reference to donation by Gregory, which is certifiably false) including the  Colorado Dragon!  Just as the tag line at the top of the blog from the Dire Straits’ song says that when two people claim to be Jesus, one must be wrong! In the case of the Gregory Gulch gold there are three competitors for the label designated 5600.

CSM 5600 with CSHS label

Number 5600 in the Colorado School of Mines display.  Note no mention of a donation by Gregory.

The photograph above shows a gold specimen on display at the Colorado School of Mines, and it carries the number 5600.  This specimen has all the documentation to suggest that it is the original 5600, although no where is there any indication that it was donated by the original prospector. This does not mean the specimen on display is authentic. There are many reasons that the Colorado School of Mines piece could be a misrepresentation — including an attempt by someone at the School of Mines to cover up trading away the original Colorado Dragon.  But that said, two specimens with the same number, and at least one of those with very questionable historical references? At the very least, one is left with a tremendous sense of uncertainty, and anger that such an important historical artifact is now tarnished. Ed Raines is the Collections Manager at the Colorado School of Mines Geology Museum, and one of the most knowledgeable professionals I know of in terms of Colorado minerals.  Ed is also a bulldog – he pursues information with tremendous tenacity, and is a stickler for facts. He understands the importance of Gregory gold, and has scoured the records to shed light on the mystery.  Along the way he found a third specimen labeled 5600, now in another private Colorado collection!  Two is bad, three is ridiculous.

Lau collection Old 5600

Another 5600! In a private collection

The picture above shows this third specimen, and its label — identical to the one with the Colorado Dragon.  This third specimen was also acquired from Richard Kosnar.  Without labels, all three golds would be interesting specimens;  with the labels they become locked in the evidence room of speculation and innuendo.  Just as labels add to the “value” of many specimens, these simple tags can cast doubt, and ultimately, disgust.  The principals in the original transactions may know the real facts, but today there is only conflicting labels and at best, duplicate specimens.  In my professional life I am asked to make judgments based on incomplete and conflicting data;  I can not conclude anything from this mess other that someone(s) behaved inappropriately.

Why do Collectors Believe?

There are untold numbers of minerals that are inappropriately mated with labels. There are obvious examples where this matching is done with malfeasance – simply mineral fraud. Every collector is also familiar with unintentional mislabeling. This usually occurs when old collections have fallen to a state of disrepair, and labels become disassociated with the physical specimens. There are many tales of collecting apocalypse where carefully nurtured and curated collections that are passed along to uninterested progeny only to end up in a garage sale (I did acquire an outstanding jalpaite thumbnail in estate sale once for the princely sum of 3 dollars!). There are also many labels that are applied to specimens based on “guesses” – some are educated guesses and sometimes they are little more than wishes and hopes (my bideauxite pictured above is now labeled Tiger, but that really is just an educated guess). Unfortunately, once a label is attached to a specimen, however indelicately, it develops some credibility. This credibility resides mostly in the hearts of collectors – it is easy to blame unscrupulous dealers, but in the end it is the collector that decides the value of a specimen. The vast majority of mineral labels are above reproach; if there is something incorrect it is usually based on good intentions (e.g., when I label bideauxite as being from Tiger — no good intention is had by labeling it from Leadville!). However, there are some startling examples where mineral pedigrees that are incredulous, yet are accepted and promoted by knowledgeable collectors. This speaks to the psychology of collectors, especially the most passionate members of the hobby. Their pursuit of minerals can cloud their judgment to point of accepting the flimsiest evidence if it means they acquire something unique.

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Barlow Chalcocite: originally sold as Jalpaite

I experienced an example of this power of wishful thinking in the early 1990s when I was asked to write a chapter documenting the silver specimens in John Barlow’s collection. John had acquired an incredible jalpaite, purportedly from the Caribou Mine, located about 20 miles west of the modern city Boulder, from Richard Kosnar. John’s later recollection of the acquisition was that he was skeptical of identification, but when I first saw the specimen in his home in 1993 he presented it as the world’s finest jalpaite – it is pictured above. Peering at the fine miniature, I reacted with typical skepticism and sarcasm – I laughed. I had seen the specimen in the pictured in the Mineralogical Record years before (1976 to be exact), but in person the specimen was stunning….just not jalpaite.  Laughing was probably not the best way to start a serious mineral discussion; nevertheless, John eventually had the specimen “tested” at the Smithsonian, and it was confirmed to be a chalcocite. It was a very fine chalcocite, but clearly was not from the Caribou Mine. John eventually came to terms with Kosnar, and decided that it was a chalcocite from Levant Mine in Cornwall, and had come to Colorado as a collectable by William Turnby, a partner in the Caribou mine back in the 19th century.  Turnby had spent time in Cornwall, thus, this became “a plausible explanation”. This is how the specimen was labeled in John’s collection when he died. Is the Barlow label believable? Not to me.

The most disquieting aspect of this story is that John Barlow was a very knowledgeable collector – why would he accept this fanciful explanation? John was not duped into his belief by an unscrupulous dealer, but truly believed he had an amazing treasure. This tale is hardly unique – many collectors have labels that they want to believe against a preponderance of evidence.

When Specimens are Historical Artifacts, not Works of Art

Mineral collecting has as many different facets as there are collectors. For many, minerals are works of art; for others, they are expressions of science. For some collectors, including me, minerals collections are ultimately an expression of humanity. Labels tell that human story. When labels go awry – intentionally or accidently, the story of a collection is diminished. Sometimes this is inconsequential, but other times, the mislabeling is historical theft.

The Zen of Stephanite: Collecting Minerals in the Era of Art

The most beautiful experience we can have is the mysterious – the fundamental emotion which stands at the cradle of true art and true science.  Albert Einstein

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A family gathering of Stephanite – Ag5SbS4 – a black and rather plain silver mineral. From the left, a single crystal from Pribram (crystal is 4.5 cm high, scale for other specimens), a cluster of bright crystals from the Husky Mine, Yukon, Canada, and dozens of prismatic crystals on matrix from Joachimstahl, Bohemia.

I have been collecting minerals for 54 years, and in that half century there has been a dramatic evolution of the “mineral hobby”. Perhaps this evolution is normal, but today the hobby is barely connected to the rock hound roots of my past. I was recently offered an incredible (a more descriptive adjective would be “obscene”) sum for one of my mineral specimens. The dollar amount was more than 3 times the annual salary I drew when I started as an assistant professor at the University of Arizona in 1983. Rather than being pleased with the offer and congratulating myself on the thoughtful investment strategy I must have concocted all those years ago, I was despondent. The collector persisted, and told me the “specimen was a masterpiece, a work of art”. Art!  Indeed I collect minerals because they are meaningful artifacts – the perfect combination of science, human history and perfection in nature, but the way the term “art” was being used reduced the specimen to the calculus of trophy hunting.

My depression was an expression of  the culmination of frustrations and fascinations with the changes in mineral market I have observed.  In the 1960s and early 70s most minerals were within the economic reach of a dedicated mineral collector. There was a “top end” to be sure, and certainly many minerals fetched prices that exceeded the cost of a new automobile.  However, there were many collectors that built incredible collections on a bargain budget.  These collectors were driven by a passion I can relate to – most were very knowledgeable about mineralogy and had a rudimentary understanding of the geology.  In the early 1970s there was a strong push by a group of mineral dealers and curators to describe some minerals as “natural works of art”. Paul Desautels was at the vanguard of this movement, and in 1968 he published The Mineral Kingdom, which is arguably the most influential mineral book in history.

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The Mineral Kingdom – a remarkably influential book published by the curator at the Smithsonian in 1968. Although perfection and beauty in mineral specimens had long been sought, The Mineral Kingdom laid out why mineral specimens should be thought of as art.

I received a copy of The Mineral Kingdom for Christmas in 1970.  I loved the book (still do) – it has chapters on the science of minerals, the history of minerals, famous localities and countless historical drawings and photographs.  It also has chapters entitled “Mineral Masterpieces” and “The Connoisseur”.  The opening soliloquy of the chapter on Mineral Masterpieces: “Classic mineral specimens, like great works of art, achieve their status through experts’ judgments”.  This sentence is, of course, 100 percent factual – and I would be very hypocritical to suggest that I don’t covet, pursue, and cherish mineral masterpieces.  However, this tie to art has driven the mineral market in the last 40 years in ways that are not healthy.  In the art world the top end of the market seems to have little relationship to driving prices and value at the low end of the market.  That is not true in the mineral collecting world – prices for top pieces provide justification for pricing lesser specimens.  The conversation goes like this:  I saw a Kongsberg silver wire that was just sold for $300,000 dollars, therefore this lesser Kongsberg must be worth at least $40,000!  In the art world no one says that a 25 million dollar Rembrandt sketch of a smiling woman means that similar drawing by Elmer Fudd justifies a price of 1 million dollars.

In my opinion mineral collecting in this era of “minerals as art” has made minerals much less accessible to beginning collectors and those of modest means.  The market place is still adjusting, and Darwinian forces will most certainly win out.  Luckily, there are still some minerals that have resisted the art trends — mostly very common minerals, very rare minerals, or those that are considered “ugly”.  Being a silver collector I am fortunate that some of the silver species fall in later two categories.  One of these is stephanite – and as Einstein notes, it is mysterious mineral, at the intersection of science and art.

Minerals as Art

There is a vast body of literature devoted to the psychology and motivations of collectors of high priced art. In truth, art collectors are probably not a lot different that collectors of “any objects” – baseball cards, model trains, stamps, coins, etc. However, there is a special aura associated with art collecting. In November, 2013 Christie’s auctioned the Francis Bacon painting “Three Studies of Lucian Freud” for $142.4 million dollars (there are rumors of private art sales for even more – $250 million for a Cezanne in 2011, for example). To me, the Bacon painting is just flat; it does not move me in any way.

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Francis Bacon’s Three Studies of Lucian Freud, painted in 1969. Christie’s sold the painting in auction for more than 142 million dollars, which 7 bidders competing for the right to own….these three panels.

142 million dollars?  Those that analyze the art market claim that the value is driven by both passion and competition.  The passion is easy to understand, but it is the competition that propels the price sky high.  Competition in this case is not the same as demand for a rare resource, although that is a factor.  Rather, the competition is about denying others the trophy.  This lust for winning strikes a deep nerve.  The ultimate trophy is an important aspect in mineral collecting today.

In 2012 the Economist magazine profiled several studies on the art market, including a Barclays Bank report entitled “Profit or Pleasure? Exploring the Motivations Behind Treasure Trends”. The report interviewed 2000 art collectors and dealers (all very rich people) from 17 different countries, and found that this rich clique had a strong sense of community. The collectors, and dealers that cater to them, shared that buying art engendered feelings of victory, cultural superiority and established a badge of social distinction. The sense of community also leads to mechanism of validation – these collectors want what the other collectors want, and were actually quite conservative in branching out on their own, and rarely are trend setters.

Art Basel is an annual art fair in Switzerland that is sort of like the annual Tucson Gem and Mineral Show. Some 300 plus very high end galleries put on a show that is a “do not miss” event for collectors and museums. In the Barclay report there were a number of dealers that talked about their strategies for selling their wares. They often make a list of people they think would be a “good home” for a piece of art, and then show the piece only to those queued on the list. Collectors that have a piece reserved for them personally are nearly twice as likely to buy the art work than if it is openly displayed in a gallery. This last year Art Basel tried an experiment of opening the art show early to select “VIPs”; lesser VIPs had to wait a few hours before they could buy. Predictably, the lesser VIPs were angry – mostly about their demotion in status.

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Ikons, a 2007 publication by mineral dealer Wayne Thompson, was a tribute to minerals as art. Thompson makes the argument that visual presence of certain specimens makes them “ikons” — as the art standard for the mineral community.

The description of Art Basel could easily be Tucson if the words “art works” and “mineral specimens” are interchanged. Today the highest end mineral specimens are sold at “pre-show” gatherings at resorts like Westward Look. The well healed arrive a week before the main show in downtown Tucson, and visit the pre-shows. They ask if dealers have anything set aside for them – and the successful dealer always has a stash hidden away, under the bed or in the bathroom, that is just to be viewed by the preferred customer. The “lesser collectors” (people like me – knowledgeable but never a VIP) then can browse the more modest minerals on the shelves of the display cases. I am told that the preferred customers account for 10 percent of the sales in volume and 75 percent of the monetary value.

In 2007 Wayne Thompson published a special volume in the Mineralogical Record. This volume was called  Ikons – Classic and Contemporary Masterpieces.  It is a homage to minerals as art, and makes the point that iconic specimens are as important at art masterpieces.  However, there is a huge disconnect between pricing for mineral masterpieces and lesser specimens.  It is always difficult to know what an “ikon” has sold for — rumors help drive up prices — but a simple example illustrates this dilemma.

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The Aztec Sun – legrandite — as displayed in the MIM museum in Beirut. This is one of the world’s most famous mineral specimens, and now is a standard for comparison for all legrandite.

One of the most famous mineral specimens in world is the Aztec Sun – a spectacular spray of lemon yellow legrandeite from Mapimi, Mexico. Today the Aztec Sun resides in a fabulous museum, MIM, located in Beirut, Lebanon. This specimen use to be in the Miguel Romero mineral collection, and I had the honor of curating the Romero collection for 5 years.  When it was decided to sell the Romero collection this piece was the subject of much angst on pricing.  How much was it worth?  I don’t know what the actual selling price was, but the rumor was 2 million dollars.  It is about 20 cm high, and really, a rather simple mineral; (Zn[AsO4] [OH].H2O).  The rumored sales price reverberated through the mineral community, and I know of at least 3 cases where a mineral dealer raised their prices on the legrandite specimens in their stock — in one case the repricing was an escalation by a factor of 3!  Why?  The specimen that suddenly carried a hefty price tag was hardly the Aztec Sun; in fact, it was a rather unremarkable 4 cm cluster of slightly damaged crystals on brown limonite matrix.  A decade later that specimen is still for sale, although now only twice its original price tag.

This dragging up in value of lesser specimens by the sale prices of the “ikons” is a perplexing problem in the mineral hobby.  It seems to suggest that a mineral species or its locality is the equivalent to a named artist – i.e., legrandite = Van Gogh.  It is difficult to know what the market trend will be for minerals – will they become mineral specimens again, or only works of art?

Stephanite

Stephanite is one of the four “common” silver sulfosalts – the others being polybasite, pyrargyrite, and proustite.  Stephanite is known from hundreds of localities, and in the past was a very important ore of silver (in fact, stephanite along with acanthite, was the primary ore at Comstock Lode in Nevada where 200 million ounces of silver were produced). Despite its relative abundance and chemical kinship to the other more highly coveted silver sulfosalts, stephanite is hardly ever considered a “classic”. A picture of stephanite has never graced the cover of Mineralogical Record, and it does not even get a tiny shout-out in Ikons. Stephanite is black, rarely lusterous, and mostly found in small crystals. However, it is a mineral with a rich history, and is an important artifact from every historic silver mining camp in the world. It well may be the antidote to minerals-as-art movement. Stephanite is where I find my Zen.

4.5 cm tall crystal from Pribram, Czech Republic.  Jeff Scovil photo.

4.5 cm tall crystal from Pribram, Czech Republic. Jeff Scovil photo.

If there was a “world class” stephanite it would probably be the crystal pictured above from Pribram, Czech.  The crystal is of extraordinary size for the species, and a bright luster.  The mines of Pribram are quite ancient – silver mining is known here from the 13th century.  During the 19th century the Pribram mines were some of the most technologically advanced in the world, and were the first to have shafts that descended 1000 meters below the surface.  The best silver species specimens were mostly mined before 1860, and are very well represented in the Narodni Museum in Prague. The pictured stephanite is the best I know of, although it is difficult to document its lineage.  Below are the mineral labels still with the specimen; it came to me through Gene Schlepp.

Labels for the Pribram stephanite.  Only the last label is recognizable to me - Rukin Jelks (who was a very highly regarded southern Arizona collector).

Labels for the Pribram stephanite. The H. Maucher label most be from the late 1930s.  Rukin Jelks (who was a very highly regarded southern Arizona collector) was the last owner before passing the specimen through Western Minerals in Tucson.

The common silver sulfosalts are part of a group of complex chalcogenides with a chemical formula AxBySn where A = Ag, B = As, Sb or Bi, and the S is sulfur. For stephanite the formula is Ag5SbS4. The fact that polybasite, proustite and pyrargyrite are part of the same group means that they all have similar properties structurally – and which of these mineral forms in a geologic environment mostly depends on temperatures and pressures. In almost all cases, the silver sulfosalts form in epithermal veins – hydrothermally driven fluids.  Stephanite is the last of these minerals to precipitate out of solution – in fact, stephanite  is not stable above 197 degrees C.  Above this temperature stephanite decomposes into pyrargyrite and acanthite.

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Stephanite on polybasite, Fresnillo, Zacatecas, Mexico.  The stephanite is the last silver mineral formed in most epithermal silver veins.

The specimen pictured above documents the paragenesis of stephanite from Fresnillo, Zacatecas, Mexico.  The core of the specimen (with is 3.5 cm high) is a polybasite crystal.  Sprinkled across the polybasite are stephanite crystals which grew on the polybasite as the vein fluids cooled.  Fresnillo is an amazing silver deposit, and source of some of the very best silver sulfosalt specimens in existence.   Mining at Fresnillo dates from Spanish Colonial time, although few specimens survived before the mid 1970’s.  Fresnillo is often mentioned as an important silver district in historical literature, but it really was quite unremarkable. The district was nearly abandoned in the 1970’s, but a desperation drilling program discovered a blind vein system a couple of kilometers southeast of the main workings.  These veins average 800 g/ton of silver, and occasionally grade to 2000 g/ton.  Seams of solid pyrargyrite 35 cm thick have been reported and individual crystals more than 10 cm in length have been collected.  The district has now produced more than a billion ounces of silver (Kongsberg only produced 43 million ounces of silver!), and exploration in the surrounding region has located huge reserves. Many of the best specimens came out in the period of time 1992-1999;  I was extremely fortunate to have seen most of the best material, and acquired the core of my collection from Dave Bunk during this time.

Stephanite was first mentioned in literature in 1546 by Georgius Agricola.  Agricola, born Georg Bauer, is the “father of mineralogy”;  he was the town physician at the Bohemian mining center of Joachimsthal, and wrote extensively on the geology of the region. In his 1546 text  De Natura Fossilium Agricola described the mineral as schwarzerz in reference to its black color.  It is later referred to with various names – both in latin and german – as black silver ore and brittle silver ore.  In 1845 Wilhelm Haidinger proposed the modern name of stephanite in honor of the Archduke of Austria, Stephan Franz Victor.  Archduke Stephan was one of many nobelmen of the time that built “natural history cabinets” — however his was just extraordinary!  He acquired more than 20,000 specimens, mainly from the mines of Bohemia.  When he died the collection went to the House of Oldenburg. Much of it was sold, but some of the specimens remain in  the Natural History Museum in Berlin.  The Archduke’s labels are distinctive, and much coveted by mineral collectors today.

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A complex cluster of stephanite crystals from Freiberg, Saxony. The specimen is a little over 5 cm tall. The specimen was originally in the Archduke Stephan collection, and has passed through at least 5 collections before coming to me.

Stephanite belongs to orthorhombic crystal class, although twining on the prism planes is extremely common giving rise to pseudo hexagonal crystals. There are three dominate habits for stephanite: (1) thin, hexagonal plates that can be as large as the size of a US quarter, (2) elgonated hexagonal prisms (like the Pribram stephanite pictured above), and (3) tubular clusters of crystals that form branching clusters.  Stephanite is iron-black in color and sometimes has a bright luster.  There are numerous mineralogical texts that claim the bright luster will dull with exposure to sun light, but I have no evidence of that, nor do I know what the physical mechanism would be.

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Stephanite prism, Fresnillo, Zacatecas, Mexico. A classic pseudo hexagonal prism, 2.7 cm tall. Some of the very best stephanotis ever recovered came from Fresnillo in the late 1990s. Jesse La Plante photography.

The largest stephanite known are from a modest mine, the Las Chispas, located near Arizpe, Sonora, Mexico.  The production history of the Las Chispas is mixed; it was interrupted by revolution, strikes and seizure. The total silver produced probably did not exceed 20 million ounces of silver, but a very enlightened mine manger, Edward Dufourcq collected specimens and the mine owner, Pedrazzini, donated many to the Columbia School of Mines.  Dufourcq wrote the following in an article published in 1910; “The crystallized specimens of the silver minerals are especially noteworthy….What is probably the largest single specimen of stephanite in the world was presented by Mr. Peddrazzini to the Egleston collection at the Columbia School of mines, where there are also a number of other specimens of polybasite and stephanite, as well as a remarkable specimen representing the transition of an argentite crystal into cerargyrite and a fine embolite. The American Museum of National Hisotry in New York also has, from this mine (the Las Chispas), what is probably the largest mass of polybasite crystals ever taken out in one piece. This originally weighed over 65 lb., but was broken into two parts during the time it was in transit from Sonora to New York”.  When I was curator at the University of Arizona Mineral Museum we received one of the two pieces of the “65 pound” polybasite crystal group in trade – it only weighed 13 pounds!  The stephanite groups are smaller than the polybasites, but still giants for the species.  The largest I know of is a cluster of crystals 12 cm across.  The photo below is a very large crystal group in my collection.

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Stephanite, Arizpe, Sonora, Mexico. A large cluster of crystals from the Las Chispas mine; the specimen as displayed is 6.8 cm across. Jesse La Plante photograph.

Stephanite has always been a favorite of serious collectors, even if it is not in “art world”.  Below is the mineral advertisement from the Foote Mineral Company of Philadelphia. Albert Edward Foote, who arguably is the most famous mineral dealer in American history, sold minerals from 1875 until his death in 1895 (the company passed to his son, a good dealer in his own right, and then to others and still exists today). The ad below includes a reference to “Stephanite, fine crystals, 75 cts to $5″ from Germany.

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Mineral advertisement from A.E. Foote Minerals published in 1894. The stephanite specimen pictured below was one that was sold with this ad, and costs $3 dollars 120 years ago.

I bought a stephanite in 1988 (pictured below) that came with a photocopy of this ad, and a note that the specimen was purchased from the ad for $3 dollars in 1894.  It is impossible to confirm that this is indeed true, but it does provide a fanciful barometer for price increases.  I bought the specimen for 450 dollars – which translates into an escalation of a factor of 150.  There are many “inflation calculators” that can help give a sense of the rising costs overall.  These calculators say that consumer goods have increased by a factor of 20 over in the last 100 years (averages 3% a year), thus stephanite has been a “good” investment. But the 3% annual inflation is highly misleading – some commodities have increased in value and others have dropped tremendously (for example, the cost of electricity).  Another way to compare the value of the price increase is to compare it to a specific commodity through time.  For a mineral collector the perfect barometer is the cost of a pint of beer (mineral collectors, in general, think in terms of specimens and beer).  Using the average price for a pint of beer in a bar in New York City in 1900, and again in 2000, the cost increase was a factor of 180 (data from the Economist). In other words, stephanite prices have not kept up with the price of beer.  This truly means that stephanite is not art!

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Stephanite, Frieberg, Saxony, Germany. A large thumbnail, originally bought from the A.E. Foote mineral company in 1894. Jesse La Plante photograph.

Mineral Collecting in the Era of Art

There are a number of ways to evaluate the value of a mineral specimen. These include rarity, locality, pedigree, and aesthetic beauty. Beyond the specific character of an individual specimen, it can have value as part of a collection, documenting the nature of a particular mine or geological deposit. Unfortunately, the evaluation criteria are highly subjective and subject to changes in mineral availability and popular notions of aesthetic beauty. In the last 20-30 years the “masterpiece” or trophy mineral has dominated the pricing paradigm in the hobby, and dramatically skewed the sense of worth.  Wendell Wilson and John White (1977) conducted an experiment in specimen appraisal by asking a group of museum curators, collectors, and mineral dealers to estimate the cost of ten different mineral specimens.  The survey was conducted twice, four years apart.  Although the time separation was too short to gauge slowly varying trends (like specimen size), it did capture the strong trends in trophy hunting. During this four-year period the average mineral specimen increased in value by 190%! Although not immediately obvious, this dramatic increase caused a cosmic shift in mineral dealing.  Dealers began to view specimens as an investment and certain new collectors demanded a high rate of return.  Those dealers that understood the trend were able to adapt the business practices of the art market.  However, this adaptation had some very unexpected consequences – all mineral prices became pegged to the highest priced trophies.  This meant that “esthetic” but otherwise unremarkable mineral specimens rose in marketing value at an unprecedented rate.  By the early part of the 2000s large numbers of collectors had either stopped buying, or were now buying specimens with much less frequency. Today, the mineral collecting hobby is changed – and will continue to change — and is no longer the bastion of “rock hounds”.  The question I am most frequently asked today is “how much is that worth”.  Almost never am I asked about why a specimen is important, or why I enjoy it.

Fortunately, I can still enjoy my hobby through scholarship, and the pursuit of a few, largely unappreciated species.  The Zen of Stephanite.

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2.8 cm prism of stephanite with white calcite crystals, from Fresnillo, Zacatecas, Mexico.

A rolling stone does gather moss; return of a silver specimen and the meaning of collecting

Truth is the property of no individual but is the treasure of all men.  Ralph Waldo Emerson

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A label from the collection of Archduke Stephan, dating in the mid 1800s

I often get asked why I collect minerals, and in general I ignore the inquiry because the answer is a thesis not a sentence.  Recently I had returned to me several silver specimens from my collection that “disappeared” for 2 years.  The conditions of the “disappearance” is a tale of poor decisions (mine), disorganization (a middle man) and opportunistic dishonesty (a mineral dealer of questionable ethics).  However, fate and friends dealt a favorable hand and the specimens were returned (although one was damaged), and my joy in return of the prodigal stones gave me a chance to explain my rationale for collecting.

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Frieberg silver wire, 6 cm high.  I acquired this specimen in 2010, and it was first cataloged in a collection in 1832.

The centerpiece of the missing specimens was a silver wire from the great German locality of Freiberg.  The specimen is a little over 6 cm high and has a patina of age giving it a glow of significance.  The specimen was first documented to be in a collection in 1832, and it passed through at least 9 different owners before it came to me.  The specimen has beauty to me, but more importantly, it is an artifact of history and humanity. This particular specimen has aesthetics, and its form is an interesting mineralogical tale. In addition it is from a mining locality that has a rich history, and once the silver wire was mined, it was a prized natural history specimen that was passed along to collectors that had the same passion as I.

Collectors:  Evolution or Illness

There are dedicated collectors in every society, and these collectors are not defined by economic or social class.  There is a large body of literature on the psychology of collecting (most of which I find pompous and over reaching!), and there are two basic schools of thought.  The first is the Freudian view that says collectors are afflicted with a compulsive disorder; collecting is emotional and a desire to control or connect.  The second view is the collecting is an evolutionary trait associated with amassing treasure as a survival instinct.  Neither of these synopses really describes the passion that most serious mineral collectors I knew feel.

The vast majority of mineral collectors I associate with feel joy in finding a natural object that has beauty and form.  There are mineral collectors that pursue specimens as investment or status.  However, they are usually of the “moneyed class”, and they represent something different that most of the collectors I know, although the first prominent mineral collectors were indeed from the rich and powerful.  Mineral collecting began in the 18th century by aristocrats – they assembled cabinets of rocks and minerals, and these cabinets were badges of social class.  Perhaps the most famous of these early aristocratic collectors was Archduke Stephan Franz Victor von Habsburg-Lothringen. Born into the Hapsburg Royal Court, Stephan was well educated, and destined to a life not sullied by common labors.  He built a mineral collection and cabinet that eventually contained more than 20,000 specimens.  The top figure in this posting is one of Stephan’s labels – there are many mineral collectors that value a Stephan label almost as much as a mineral.  The stephanite specimen below is also from Freiberg, and was once in the Archduke’s collection.  Stephanite is named for Stephan.

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Frieberg stephanite, 7 cm high, acquired in 2008.  This is an extraordinary stephanite crystal group, and has spent part of its “life” in two museums and three private collections before coming to my collection.

Collecting Silver

I first started collecting minerals at age 4 or 5, fostered by the passion of my father who loved collecting minerals in the field.  At least a couple of times a month we would journey to mines or mineral localities in New Mexico, Colorado or Arizona.  I can’t really say why my father was such a dedicated field collector – he was a chemist by profession, but the science of minerals did not seem to be what was important to him.  He was raised in the home of his grandfather who was a prospector in Arizona, and this man seemed certain that the next great lode was hidden in the deserts and rugged mountains of Arizona just waiting to be discovered.  This lust of treasure hunting more describes my father’s passion – he was not really looking for the mother lode, but he loved finding a great specimen in the ground.  Once we got the rocks home he was far less interested in them – the pursuit was his passion.  He built an extraordinary library for topographical mineralogy – boxes and filing cabinets filled with Xeroxed reports and papers from obscure journals.  He assembled this material to map out where to go and collect next.

My brothers and sisters often accompanied my father on our journeys through the southwest.  However, none of them became mineral collectors, nor even really dabbled in collecting.  Clearly, mineral collecting is not a simple matter of nurture.  My first mineral collections were mostly driven by form – I loved euhedral crystals with sharp faces.  By age 10 I had a catalog for my collection that numbered in the several hundred; within a few years after that I was actively trading many of my specimens with a dealer in Albuquerque in an attempt to acquire “better” material.  In high school I had my first serious cull of my collection after which I would only collect sulfide ore minerals.  I had a very fine collection of galena, pyrite, chalcopyrite and a few chalcocites!

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Freiberg acanthite, 5.5 cm high.  This specimen was acquired in 2002, and has been pictured in numerous publications

I continued to refine my collecting until the early 1980s when I decided to only collected silver minerals.  Although I am interested in nearly all minerals, my focus is quite narrow.  There about 4600 different mineral species known, and approximately 160 of them have silver as an essential element; of these, only about 15 are “common” or available as crystals that are easily seen with the naked eye.  Silver has been reported from more than 20,000 localities world wide – approximately 100 different localities have produced quantities of very well crystallized specimens of the common silver species.  In my collection today I have samples of 109 of the different silver species, and I have every important locality represented.

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The wire silver from Freiberg is a quintessential specimen from my collection.  The Erzgebirge are a modest mountain range that runs along the boundary between southeastern Germany and the northern part of the Czech Republic) for about 100 km.  The English translation of Erzgebirge is “Ore Mountains”, and these rolling hills are the birth place of modern mining, metallurgy and mineralogy. The German side of the Erzgebirge is known as the Saxony side, while the Czech side is referred to as Bohemia. The Bohemia mines of fame include Kutna Hora and Jachymos/St. Joachimsthal, while the Saxon mining areas of note are Schneeberg and Schlema, Annaberg, Marienberg, Johanngeorgenstadt, and the most famous of all, Freiberg.

The story of the Erzgebirge silver is voluminous topic; a simple summary of Freiberg serves to at least stake the claim of the Ore Mountains as being the most important silver mining camps in history.  Silver was first discovered in Freiberg in 1163 – the area is located about 30 km west-southwest of Desden.  The town was officially founded in 1186, and over 800 years of mining produced about 8 kilotonnes of silver.  The two most famous Freiberg mines are the Himmelfahrt and Himmelsfurst – these were large mines with multiple shafts.  The enduring influence of Frieberg came with the founding of the Bergakademie Frieberg, or Frieberg Mining Academy, by Prince Franz Xaver in 1765. The mining academy in Freiberg can now lay claim to the oldest School of Mines, and can lay claim to educating some of the most famous mining engineers and mineralogist in the world.  A.G. Werner, a mining geologist on the faculty first proposed a chemical classification of minerals in 1774 – he invented the modern scheme for describing minerals. The Frieberg Academy had a profound effect on mineralogy also be preserving specimens that came from the mines and build a remarkable mineral collection.

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Freiberg silver, 7 cm high, acquired in 2001.  This is a classic example of wire silver that must have grown from the decomposition of acanthite.  The wires have been exposed by removing the encasing calcite.

I had the chance to visit the Freiberg Academy in the summer of 1991.  The Berlin wall had just fallen, and East and West Germany had reunified.  It was clear as I drove from Frankfurt to Dresden that there really were two Germanys.  The infrastructure in the east was third world, and as I drove through Dresden there still were Soviet tanks deployed.  However, when I got to Freiberg, the Academy staff were incredibly warm and helpful.  What I saw in the collections was amazing, and made my connection to my Freiberg silver minerals much richer.

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Freiberg Pyrargyrite, field of view is 1.7 cm.  This specimen was acquired in 1984, a came through a dealer that had traded it out of the American Museum of Natural History in New York.  The AMNH is one of the great mineral museums in the world, and received the collections from the Columbia School of Mines in the early part of the 20th Century.

Silver has an affinity for anions of sulfur, selenium and tellurium, all of which have similar ionic radii.  These minerals are known as the silver sulfides (in the nomenclature of Dana, these include the tellurides and selenides), of which the acanthite group is the most common.  The acanthite group includes the simplest sulfides (the most common of these are acanthite, argentite, aguilarite, naumannite, hessite, petzite, empressite, jalpaite, stromeyerite and eucairite).  This group of minerals displays the characteristic of temperature-dependent dimorphism.  At high temperatures these minerals are usually cubic or hexagonal, whereas at lower temperatures the minerals display an orthorhombic or monoclinic crystal structure.  The transition temperature is usually between 130 and 180o C.  Acanthite and argentite are the most common dimorphic pair.  Acanthtite is the form that is stable at room temperature, so even when a specimen appears to have cubic crystals, it is a monoclinic microstructure frozen in the cubic frame.  The same thing that makes the silver-sulfur bond temperature dependent also makes acanthite sensitive to decomposition when temperature and pressure change – silver is released from the sulfur bond and grows wires out of the acanthite.  Silver wires are extremely common, and it is clear that they are all formed by the decomposition of a silver sulfide (most likely acanthite).  This was first observed and understood at Freiberg.

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An early explanation for the growth of silver wires by the decomposition of acanthite

The rest of the story of the mineral mystery

I have wanted to write a book on the silver minerals for a long time.  Gloria Staebler has provided me the encouragement to pursue this book which will be years in the making.  Along the way I decided to illustrate certain aspects of the mineralogy with pictures of many of my specimens.  Photographing minerals specimens is not easy under the best of circumstances, and silver minerals are extremely difficult.  Their dark color, intergrown crystals, and occasional high luster means that most attempts to capture their beauty with a camera result in images that closely resemble black ink blots.  With this in mind, I sent a subcollection of the specimens to be photographed by one of the best mineral artists in the world.  However, sending multiple specimens to be photographed far from my immediate control was a poor decision.  It took several attempts to get the images right;  over time one small box of the specimens are returned to the wrong owner.  Although I did not get back my specimens there was no documentation that I did not get back these back – in fact, many people assumed I simply had misplaced them.  I knew that was not the case, but I was frustrated in locating the silvers.

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Advertisement in the Mineralogical Record that featured my Freiberg silver. Read the ad – this is what is wrong with mineral collecting today.

In late February of this year I received the March-April issue of Mineralogical Record.  As usual, I first read the most interesting article to me, and then thumbed through the rest of the volume looking at advertisements from various mineral dealers.  As I turned the pages I was stunned – there was a picture of my Freiberg silver in the ad of dealer for sale.  I was outraged!  Indeed my specimens had been returned to the wrong owner, but that dealer chose to assume that mistake was fortuitous!  Found wealth!  The repatriation was emotional and messy, but I am reminded again that honesty is a rarer commodity than it should be.  The fortuitous dealer claims that he did nothing wrong at all – in fact, he simply just thought the minerals were his, and he had forgotten how he got them.

This story is not done, but in most ways the universe is again right.  However, the story of a mineral lost is also a tale about collectors and the mineral hobby.  When I first started in the hobby more than 50 years ago it was different.  There were far more scholars than today. My sense is that this is not because there is less interest in mineralogy, but because the opportunities to build a meaningful collection are greatly diminished.  Prices have escalated – this is always true in collectables – but in a very dramatic way collecting is out of reach for the person of average means.  I have benefited occasionally from this “art pricing model”; specimens I bought for hundreds of dollars I have traded or sold for 100 times purchase value.  New collectors do not have the “hundreds of dollars” specimens available to trade or sell to better create a collection, and thus, they tend to drift away.  The case of the dealer wanting to sell my “fortuitously” purloined silvers is symptomatic of the commercial side of the collecting equation.  Not something to be happy about, nor do I see an enlightening horizon.

Stories in Stone: Mineral Collecting and the Tucson Gem and Mineral Show

A rock or stone is not a subject that, of itself, may interest a philosopher to study; but, when he comes to see the necessity of those hard bodies, in the constitution of this earth, or for the permanency of the land on which we dwell, and when he finds that there are means wisely provided for the renovation of this necessary decaying part, as well as that of every other, he then, with pleasure, contemplates this manifestation of design, and thus connects the mineral system of this earth with that by which the heavenly bodies are made to move perpetually in their orbits. James Hutton, the Father of Geology, 1795

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Moon Rise over the Catalina Mountains — Start of the Tucson Show, 2014 (photo, Michelle Hall)

One of my very first memories — vivid in my mind but probably a mixture of early experiences – is collecting topaz crystals with my father in west-central Utah.  Today, I know we were at Topaz Mountain, but my childhood memory is an image of a sandy wash on a cold winter day.  I was probably 4 years old given that my father was on temporary duty away from Los Alamos and working at the Dugway Proving Grounds.  My father had made a couple of screens, and we were shoveling the sands of the wash on to the screens and sorting through the leavings for nearly colorless topaz crystals.  We found then by the bucket load, and I remember holding in my hand dozens of crystals that sparkled brightly in the sunlight.  I don’t really remember what I was thinking when I held those crystals, but I have been collecting minerals ever since that trip.  In the 54 years or so since that memory I have searched through a thousand mines in the western US for minerals, built a dozen collections, made large rock gardens, sold thousands of minerals to buy a few hundred, and visited every mineral museum I could find in the world.  I discovered mineral shows in the 1960s, and in 1973 my father and I went to our first Tucson Gem and Mineral Show.  It was an amazing experience for me – we first went to the Desert Inn, and I could not believe the array of minerals for sale on the top of beds in a hotel!  However, it was the main show that hooked me forever.  On the show floor were special exhibit cases, and one of the very first we visited was Harvard case, which contained what I think, is the world’s most famous mineral:  a 5-inch tall “ram’s horn” of gold from Colorado.  I was spell bound!  And right next to the gold was cerussite from New Mexico that was so much better than anything I had ever seen from my home state that I was in disbelief.  I have not missed a Tucson show since that time!

The experience of that first Tucson Show had a profound effect on me, and it is fair to say it shaped my life.  I went to New Mexico Tech for my undergraduate degrees, and many weekends were spent collecting minerals from all over New Mexico – these were the seed corn to my personal collection.  Every February I would load up my pickup with the spoils of my efforts and head for Tucson. I would sell everything (for a lot less than I hoped) to a couple of dealers in motel rooms, and then use the money to buy 5 to 10 minerals for my collection.  Nothing was easy, but 1970s were a far different time, and there were many mineral dealers interested in good, colorful low-end specimens in bulk.  I still have 3 specimens that I purchased in those heady days.  When I graduated from Caltech in 1983 with a degree in seismology I had 4 different job offers, but there was only one that I wanted – a professorship at the University of Arizona.  I am a bit embarrassed to say that I based my career choice not on scholarly reputation, but rather on the opportunity to live at the center of the mineral collecting universe!

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Catalogue number 1 in my present collection – a wire of silver from Kongsberg purchased at the Tucson show in 1978

The 2014 Show

 2014 is the 60th Anniversary of the Tucson Gem and Mineral Show.  Every year they have a theme, and this year in honor of the 60years of bringing thousands of collectors from around the world to southern Arizona, the theme is “Diamonds, Gold and Silver”.   The theme serves as a focus for special exhibits on the show floor, and I committed to put in several cases of my minerals and help organize a community display (in general, I do not like to display my collection – in fact, I don’t particularly like to show my minerals even in my own home).

Since the mid-1980s I have exclusively collected silver and silver minerals.  Although I enjoy mineralogy and mining in general, silver is my passion.  Else where I have written about silver: “For many collectors, the word conjures up images of baroque ropes of white, lustrous metal from Kongsberg or beautiful herringbone plates from Batopilas.  For other collectors, the vermillion red of a Chanarcillo proustite is  the most alluring color of all specimens.  Silver and silver-bearing minerals are part of the nobility of the mineral kingdom; no other group of minerals has more associated mining lore or history.  Silver financed empires and great wars. Silver is said to have magical purifying properties, and alchemists promised secret processes to turn lead into silver (both of these myths are partially true!).  To the mineral collector, silver minerals hold a particular fascination.  Superb specimens are known from hundreds of localities worldwide, and unlike gold, silver is quite a reactive element, forming more 160 different silver-bearing elements”.

I brought minerals for two cases:  one focused on native silver and acanthit group minerals (acanthite has the formula of Ag2S, and the acanthite group minerals include some substitution for silver like Japlaite and Sylvanite, and there are also substitutions for sulfur including tellurium and selenium for Hessite and Naumannite ), and the other focused on pyrargyrite, proustite, stephanite, polybasite, and handful of other silver minerals that were some of the best of their kind.

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In front of my two cases – (1) silver and acanthite minerals, and (2) common silver sulfosalts

The Silver and Acanthite Case

Silver owes is wonderful qualities to its placement on the periodic table. Silver has an atomic number of 47, and sits below copper and above gold.  These two metals are in many ways similar to silver, but they show relatively more and less mineralogical diversity. Gold is heavier and a larger atom, from which it is more difficult to remove electrons.  Thus, gold tends to stay mainly in the native state or form semimetallic compounds with tellurium and silver.  A copper atom, on the other hand, is smaller than an atom of silver and can readily give up either one or two electrons in the process of forming compounds. This allows for the formation of many more copper minerals than silver minerals including copper silicates and carbonates. All three metals have similar atomic structures, which is a face-centered cube held together by metallic bonds.  A characteristic of a face-centered cubic lattice is that the metals are extremely malleable and ductile as well has good conductors of heat and electricity. Silver has the highest conductivity of the metals. Native silver has a bright white color; it has the highest reflectivity of any metal in the visible spectrum, and thus appears to “shine”.

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Silver is relatively abundant but dispersed in the Earth’s curst.  Magmatic activity concentrates silver, and the vast majority of silver deposits are related to volcanic activity

When not in its native form, silver is generally monovalent (Ag+1).  The silver atom has an affinity for anions of sulfur, selenium and tellurium, all of which have similar anionic radii.  These silver minerals are known are silver sulfides (in the nomenclature of Dana, these include the tellurides and selenides), and are the most important ore minerals for silver.  The acanthite group is the most common and simplest of the sulfides.  This group includes acanthite, argentite, aguilarite, naumannite, hessite, petzite, empressite, jalpaite, stromeyerite and eucairite. This group of minerals displays a remarkable structural phenomena called temperature-dependent dimorphism.  At high temperatures these minerals are usually cubic or hexagonal, but at lower temperatures these minerals exhibit orthorhomibic or monoclinic structure.  The transition temperature is usually between 130o and 180o C.  Acanthite and argentite are the most common dimorphic pair, and most specimens of acanthite seen in mineral collections show a cubic or octahedral habit “frozen” in at the higher temperature of formation.

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Silver Sulfosalt case

The “common” silver sulfosalts Case– proustite, pyrargyrite, stephanite and polybasite 

Silver sulfosalts are the most beautiful group of silver minerals.  The sulfosalts are composed of silver, lead, and copper as cations and at least one semimetals (arsenic, antimony, or bismuth) linked with sulfur in anionic groups.  Two of these sulfosalts are proustite and pyrargyrite are known as the “ruby silvers” because of their translucent red color.  In the ruby silvers the anionic group is either AsS3 (proustite) or SbS3 (pyrargyrite), arranged in a trigonal pyramid.  The semimetal is at the apices of the pyramid, with the sulfur atoms at the base.  Silver atoms connect the group in such a way that each sulfur atom has two nearest silver atoms.  Both proustite and pyragyrite are light sensitive; exposure to certain wavelengths of light break one of the sulfur bonds and liberate a silver atom that migrates to the surface of the crystal face.  Over time ruby silvers become black, which is the result of a thin silver coating on the crystals that quickly reduces to acanthite.

Although there are more than 160 silver bearing minerals, only about a half dozen are relatively common in macroscopic crystals.  The simplest of the silver minerals belong to a group called the silver halides, which are ionic bonds between silver and C, Br, or I. The largest number of silver minerals are sulfosalts (including proustite and pyrargyrite) with more than thirty distinct species.  The two most common in crystallized specimens are stephanite (Ag5SbS4) and polybasite (Ag16Sb2S11).

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A family of prostate crystals from the sulfosalt case — very hard to get the red right, but great crystals one and all.

The Kongsberg Case

I also organized a community case on Kongsberg, which is the most famous locality for native silver in history.  When silver was chosen as a theme for the show I knew we had to put together a case on Kongsberg.  I volunteered to get a couple of the famous collectors to commit to bringing a few specimens to be put in an exhibit.  The fraternity of silver collectors is relatively small, and we all know each other.  It was easy to get people to commit — but it was harder to get the contributors to limit the number of specimens that they brought!

Highlights of the Show

The MAIN Tucson Gem and Mineral Show is always an event.  The show lasts 4 days, and the Tucson Convention Center and Arena is filled with mineral, gem, fossil and jewelry dealers along with spectacular special exhibits and seminars and talks.  The public paid attendance is about 35,000, but the actual attendance with dealers, exhibiters, students and guests is probably about 50-55,000 people.  Anyone that is a serious mineral collector comes to this show, and it is very international. It is fair to say that most of my closest friends are in this community, and the common interest of things “mineral” creates a strong social fabric.

The opening of the show on Thursday is a mad rush – and mostly serious mineral people.  Within an hour the floor is swarming with people looking through dealers stock, and after that, cruising the special exhibits looking at the treasures that come from around the world. My experience is that not too many minerals are sold on Thursday, but lots of decisions are made.  Those decisions are consummated on Friday and Saturday (and for the most part, the mineral community believes that all sales are negotiations, so serious work is needed before minerals exchange hands).

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11 am opening day at the Tucson Show, one hour after the doors opened.  This is the booth of my friends Dave Bunk (Dave Bunk Minerals) and Gloria Staebler (Lithographie).

Every year the most asked question is “what’s new for this year”, meaning what new mineral discovery has happened in the last year and is marketed in Tucson.  This year the biggest news are some extraordinary azurite crystals from Milpillas.  Milpillas is a  copper mine in Sonora, Mexico, across the border from Bisbee, Arizona.  Milpillas mining operations entered a zone of carbonate rocks in 2006, and wonderful copper carbonates flooded the market. The quality was on par with the best ever – similar to Bisshee from the turn of the 19th/20th century and Tsumeb in the mid-20th century. About 2 years ago the oxide zone was exhausted, and it seemed that the Milpillas era had come to an end.  The mining begin in the sulfide zone and the milling operations were altered to reflect the sulfide feed stock.  However, six months ago the mining encountered a fault zone that had allowed the carbonate mineralization to occupy a sliver within the sulfide zone.  It seems that mining management turned a temporary blind eye to the miners collecting the fault zone since the milling process was already adjusted to a different chemistry, and some truly extraordinary azurites have come to light.  In my opinion these may be the finest azurites in history;  however, thee are thousands of pieces for sell, so there is a psychological numbness to importance of this mineral find.  Ten years from now the entire mineral community will talk about the “great old days” for azurite crystals.

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 Milpillas azurite in Evan Jones’ booth at the Tucson Gem and Mineral Show.

My favorite part of the show is the special exhibits.  It is like visiting museums and great private collections from across the world.  There were great displays on the theme – diamonds, gold and silver.  One of the many surprises was the Smithsonian display on diamonds.  They literally had a pile of diamonds that had been confiscated from smugglers that get turned over to the museum.

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Pile of diamond — the Smithsonian Institution.

There are more than 130 exhibits, and the vast majority are wonderful.  A couple of the exhibits were very unusual though and caught my eye.  For 4000 years mankind has been carving gemstones and minerals for decorations.  We have a fascination with the natural beauty of stones and the perfection of nature to present color and form.  One of the cases that I really liked this year had polished slabs of rhodochrosite and malachite  – pink and green.  These slices were cut from stalagmites, and the concentric rings are not unlike the growth rings in a tree.  The display matched the size for these stalagmites to make for a stunning display.

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Slices of rhodochrosite and malachite.

The University of Arizona Mineral Museum had several displays, all very good.  However, one had special meaning to me — gold, silver and platinum from the Hubert C. de Monmonier collection.  This was the last major donation I worked on as curator of the Museum, and is a fabulous, eclectic collection built over a life time.  Hubert was a man of modest means but he built a world case collection;  871 mineral specimens  including 350 quartz specimens, 146 tourmaline, 44 silver, 38 beryl and more than 70 gold specimens.

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Gold and platinum from the University of Arizona Mineral Museum.

Another favorite case for me was assembled by Dave Bunk to show the best of Colorado silver.  There are three mining districts in the state that stand out:  Aspen, Creede and Leadville.  The two former districts have produced the bulk of notable specimens.  Dave collected specimens from private collections (his own, Bryan Lees and Ed Raines in particular) as well as the museums at the Colorado School of Mines and the Denver Museum of Natural History.

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Included in the case were some historic artifacts — a vase made from Aspen silver, and a chunk of the largest silver “nugget” found at Aspen (it is the block in the upper right hand corner of the picture of the case).

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Smuggler Mine silver “nugget” found in 1894 weighing 1840 lbs. The Dave Bunk display contained a piece that weighed about 5 pounds!

Finally, a case that I really enjoyed celebrated birth of modern crystallography under one of the founders of mineralogy, Abraham Gottlob Werner. Werner was born into a mining family, and he studied mining (and law) at Freiberg, which is an grand locality for silver and silver minerals.  In 1775 he was appointed an instructor at the Freiberg Mining Academy, and he published the first modern textbook on descriptive mineralogy, Von den äusserlichen Kennzeichen der Fossilien. The case displayed a collection of wood crystal models that were hand made to illustrate the various classes and forms.

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The wood crystal models created at the direction of the father of modern mineralogy.

The Tucson Show is always an experience – educational, social, and even spiritual.  This year’s show is special for its exhibits.  Although the sense of wonder that I had when I first went to the show in 1973 can’t be duplicated, the show still is grand on an international scale.  Tucson itself is fabulous in its own way with a unique flora and fauna, and skies that are magic in the winter.  Still much show to go in 2014, but it has already been a great event.

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Close of the 2014 Tucson Gem and Mineral Show.  Sunset behind Wasson Peak