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.

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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

 

History Locked in Stone: Why Hessite is a Noble Mineral

Every block of stone has a statue inside it and it is the task of the sculptor to discover it — Michelangelo

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One of my favorite places to visit is the Naturhistorisches Museum Wien (Natural History Museum of Vienna).  As far as natural history museums go, it has to be the most important in the world.  It has display space of 8,500 sq meters (about 94,000 sq ft), and it is filled with more than 30 million objects.  The exhibits are decidedly old school: instead of modern interactive computer screens meant to entertain, there are taxidermy marvels documenting the discoveries of the great 18th and 19th century naturalists that explored the world as scientists. There are great fossil finds, meteorites, and stone-age works of art, and of course, there is a fantastic collection of minerals!

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The museum was built to house the collections of the Habsburg Empire.  The House of Habsburg ruled much of eastern Europe between the late 16th century and World War I. Emperor Franz Joseph I is credited with creating the museum in the mid-19th century, and the present building opened its doors in 1891.  The core of the mineral collection is from the great mining regions that the Habsburgs controlled—Bohemia, Hungary, Austria, and what would become Romania.  The oldest specimens were acquired by Archduke Ferdinand II, assembled in what is known as the “Ambrasian Collection”, and brought to Vienna in 1806.

To me, the minerals from the great Eastern European mining centers are masterpieces.  Not only are they fine aesthetic specimens, but they are also artifacts that capture human history.  Just as Michelangelo spoke of “releasing” the great artwork contained within a block of marble, the minerals that were collected out of the mines of Pribram, the Harz Mountains, Freiberg and Tyrol contain the stories of empires, miners, the birth of mineralogy, and the passion of collectors.  Life was hard in the mines, backbreaking, dangerous work with a single goal—to produce bullion.

In Europe the rise of interest in natural sciences meant that unique specimens were preserved starting in the late 18th century.  These specimens went to the collector cabinets of scientists and wealthy gentlemen.  The specimens were studied and catalogued; eventually they made their way to museums or other collectors who added their labels and love, until today we have lumps of silver or gold ore that tell a human story.  The tradition of collecting minerals from the mines was not passed to America until the latter part of the 19th century.  The mines on the Comstock Lode on the eastern slope of the Sierra Nevada were some of the biggest silver producers ever; but they were discovered in 1859 and exhausted in about 20 years, so the number of documented specimens from the Lode is remarkably few.  It is hard to imagine what mineral collections would look like today if the Comstock had been located in Bohemia.

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My favorite mineral in the museum is a spectacular cluster of hessite crystals, with associated quartz crystals.  The specimen vaguely looks like a hand with the two fingers extended.  The overall length is about 10 cm.  Hessite is a silver telluride (Ag2Te) and usually is a dull gray.  Hessite forms in medium or low temperature hydrothermal veins and is fairly widespread but almost never as crystals or even recognizable masses.  What makes the Vienna piece so amazing is that the crystals dwarf most others in the world.  The specimen is from Botes, Romania. There is a relatively small series of mines in the “Golden Quadrilateral” in Transylvania that for a few short decades produced a quantity of hessite that is unequalled in quality.  In fact, Botes hessite is so outstanding compared to other localities that it is often considered a “single locality” mineral.

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The northwestern quadrant of Romania is known as Transylvania, a high plateau surrounded by mountains.  Upon hearing the name “Transylvania” the average person has visions of vampires and Dracula; however, to a serious mineral collector the name evokes visions of spectacular gold specimens, rare gold tellurides, and absolutely amazing hessites like the one in the Vienna Museum of Natural History.  The “Golden Quadrilateral” is a region shown in the figure below that defines the largest gold resource in all of Europe.  More than half of the gold ever mined in Europe came from within the 500 sq km of the Quadrilateral, and it remains the continent’s largest gold reserve.  Along a north-northwest trend near the ancient town of Zlatna are a series of amazing deposits in the Apuseni Mountains.  These deposits are calc-alkaline volcanic centers that are the response to the collision of Italy to Europe.  The volcanoes were active between 15 and 2 million years ago.  The map below shows these centers in orange, one of these is marked with a “B” which denotes a modest mountain known as Botes Hill.

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Mining for gold in the Apuseni Mountains started at least 2,500 years ago.  Analysis of gold artifacts found throughout the ancient world, including Troy and Egypt, indicate an origin from the Apuseni deposits.  Before the Roman Empire, the region was known as Dacia; Emperor Trajan conquered the region in 106 AD.  The Romans sacked the Dacian Royal Treasury and hauled off more than half a million pounds of gold and twice as much silver.  Presumably, this wealth was originally mined from Apuseni.  The mining center during Roman times was Ampulum, which became the modern town of Zlatna.   The region bloomed again as a mining center in the 19th century when the area was under control of the Habsburgs.

The Golden Quadrilateral is rich in tellurium; in fact, the element was first described from samples of native tellurium from here in 1798.  Many gold and silver tellurides were first described from here, including krennerite, nagyagite, petzite, stutzite, muthmannite and museumite.  Hessite was actually first described in what is modern Kazakhstan (and named for a German chemist that described the mineral in 1829), but by far the best crystals are from Botes.  There is very little written on the history of Botes.  This is mainly due to the fact that it was a modest mine in terms of metal production, but in terms of hessite production it was truly remarkable!

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I have 5 hessites from Botes.  Most are like the specimen above—a cluster of crudely cubic grey crystals on matrix with quartz (and usually a little sphalerite). To many modern collectors this specimen has limited aesthetic appeal; however, every one of these specimens has a series of old catalogue numbers and labels written by the hand of long deceased collectors.  Botes only produced hessites for a relatively short period in the second half of the 19th century; all five specimens are “related”.  My favorite hessite (pictured below) is a cluster of elongated crystals (the largest blade is 1.4 cm) on a sliver of matrix.  The hessite crystals have blebs of gold on their surfaces.  The original mineralogical explanation for this assemblage was that petzite (petzite has a formula of Ag3AuTe2, simplistically, a gold atom substituting for every fourth silver atom in hessite) was intergrown in the hessite.  However, the most modern explanation is that the gold is actually intergrown directly in the hessite.  Either way, the gold blebs are a unique signature.

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A visit to the Vienna Museum of Natural History is a reminder to me of why I collect minerals.  The minerals are magnificent recorders of past geologic events—ancient subduction zones and strata volcanoes, erosion and rearrangements of continents.  At some point the veins that carried the minerals were discovered by a prospector, and eventually mined.  Some nameless miner decided to collect a piece of unusual ore, which, in turn, made its way to a collector.  Through the years that mineral resided in display cabinets or wooden drawers in storage racks, and may have changed hands many times.  Scientists may have studied the sample and recorded the crystal structure or detailed the chemistry and postulated the theory of formation.  Today that specimen—a story in stone—is in my collection, but only as a temporary resting place until to passes to the next collector.