ARTINITE CRYSTALS SPICE UP A QUARANTINE DAY

Learn from yesterday, live for today, hope for tomorrow. The important thing is not to stop questioning.  Albert Einstein

Here it is again--another day of self quarantine at the local ranch.  I should not complain since my family and friends are well and safe, but....... My adopted state of Wisconsin is going crazy with Covid-19 and friends tell me the hospitals are full and ICUs overflowing.  The Governor and Legislature continue to fight.  The Black Hills state of South Dakota has the highest rate of Covid-19 per capita in the U.S.  I remain concerned about friends in each state.  Here in Colorado the number of infected persons is increasing; however, nothing on the order of Wisconsin.  As desert, I am very tired of politics and can't wait until the election is over.  But, by January 1st campaigning will begin for the mid year congressional elections!  Yep, you guessed it--I am an old curmudgeon.

We have always held to the hope, the belief, the conviction that there is a better life, a better world, beyond the horizon. Franklin D. Roosevelt

In my last Posting I noted that desautelsite was collected from the Artinite Pit in San Benito, County, California, where artinite is a major mineral found in the excavation.  The locality is part of the New Idria Mining District located in the Diablo Range (part of the California Coast Ranges). The District contains mercury-, chromium- and magnesium-rich rocks associated with a large intrusive body of serpentine.  The mercury mines (mostly cinnabar ore) reached their heyday during the massive gold mining in California, AKA California Gold Rush, as mercury was used to extract the gold from the ore.  Mercury is mixed with crushed gold bearing rocks, or placer sands, and the gold will dissolve into an amalgam.  The mixture is then heated driving off the mercury vapors leaving behind fairly pure gold.  Of course, the mercury vapors got into the air, soil, water, and living organisms creating numerous environmental problems.  The use of mercury did not stop until the 1960s but fish in some streams, such as the Sacramento River, still carry elevated levels of mercury.     

Today the Mining District is best known for the gemstones (benitoite is the State Gem) produced at localities like the Dallas Gem Mine and the Benitoite Mine. Numerous other mines and claims are operated as specimen mines yielding a variety of minerals from garnets to serpentine (the State Rock) to gold to artinite to neptunite and others.  The District is the Type Locality to at least 15 minerals.

In my small collection I have four specimens of artinite {Mg₂(CO₃)(OH)₂-3H₂O)] purchased at various times over the years.  All were collected at the Artinite Pit.  This excavation is associated with the New Idria serpentine body where the secondary minerals, such as artinite, are located in fractures and cracks as the result of low temperature metamorphism of serpentinized ultrabasic rocks from the Earth’s mantle.

Crust of artinite botryoids on serpentine matrix. Width FOV ~8.9 cm. 

Masses of acicular crystals from specimen shown above.  Width FOV ~7 mm.

Mass of artinite silky fibers.  Width FOV ~7 mm.

This large botryoid of acicular is attached to the same specimen as desautelsite described in the previous post.  Width FOV ~7 mm.

Spray of acicular crystals.  Width FOV ~7 mm.

Although artinite is a colorless or white mineral it is actually quite spectacular when viewed under magnification as the individual crystals are acicular and usually form spherical aggregates of radiating individuals.  Others may form botryoidal clusters of silky fibers. The crystals are quite soft at ~2.0-2.5 (Mohs), have a silky to sub vitreous luster, and are transparent.  The crystals are quite brittle, and specimens must be handled with care.  Their morphology, and association with serpentine allows for identification. 

Mt. Bierstadt 14,065 feet. Hope is the pillar that holds up the world.  Hope is the dream of a waking man.   Pliny the Elder

DESAUTELESITE AND ZOOMING WITH THE MICROMOUNT SYMPOSIUM

 I had a new mineral experience today (October 10). No, not an estate sale, backyard sale, or field trip but a mineral symposium via Zoom™. Now Zoom is the new wonderkid on the block that virtually no rockhound was familiar with 10 months ago.  Now churches are holding Zoom meetings, schoolkids are attending classes via Zoom, and many businesses are essentially operating via Zoom.  Zooming is now a verb and I assume Zoom will be the word of the year (or perhaps Covid or Coronavirus).  I did insert a trademark sign ™ after my first use of the word since I presume it is propriety; however, its use these days is similar to xerox (a verb used to indicate any photocopying) or coke (a noun to indicate any soft drink). At any rate, I attended a Zoom meeting—the Desautels Micromount Symposium.

I had known about the Symposium for years, mostly from reading Quintin Wright’s yearly review, “Through the Scope: The Year in Micromounting” published each year in Rocks and Minerals.  However, the Symposium is sponsored by the Baltimore Mineral Society and Maryland is a fair distance from Colorado Springs, so the Zoom meeting was a blessing in disguise, at least for me. The regular attendees were “OK with the format considering the Covid situation” but were missing the camaraderie, the specimen trading, and especially the give-away tables.  I certainly was an outsider, but no one could recognize me since my new webcam could not, or would not, (blame it on the electronics) post my video photo online! So, I was just Michael on the screen.  However, they are a friendly bunch and certainly would have welcomed me if I would have appeared 😊

The Baltimore Mineral Society was established in 1951 (CSMS dates to 1936) and is a member of both the Eastern Federation and the American Federation.  This year the Micromount Symposium celebrated its 64^th annual event (if I count correctly) and this was the first Zoom event! The official name is the Desautels Micromount Symposium named for Paul Desautels, a famed micromounter.  I am uncertain when that moniker was applied to the Symposium.

The Bibliographic section of the Mineralogical Record website (mineralogicalrecord.com) has a very inclusive biography of Desautels and a few points are extracted below. Desautels (1920-1991) held many professional positions in his career but perhaps is best known for his 25 years spent as Curator of Gems and Minerals in the Department of Mineral Sciences in the U.S. National Museum of Natural History, AKA Smithsonian Institution. In fact, he was “the most influential curator of the 20^th century.” Desautels was awarded the Carnegie Mineralogical Award for his mineralogical contributions, the Smithsonian Director’s Medal, and the Tucson Gem and Mineral Show created an annual award for “mineral collecting connoisseurship” named the Desautels Trophy.

The Micromounters Hall of Fame was established by the Baltimore Mineral Society to honor those who have supported and promoted micromounting.  In the early years, the Society honored “modern awardees” and a few “old timer awardees.”  In 1981, the initial year, Paul Desautels was inducted along with “old timers” George Fiss (d. 1925) and George Rakestraw (d. 1904). In examining the Hall of Fame recipients I noted the names of Lazard Cahn, 1982, the Honorary President for Life of CSMS, Arthur Roe, 1993, a founding member of CSMS who studied under Cahn, Jim Hurlbut, 2011, from the Denver area and a force in the Rocky Mountain Federation, Shorty Withers, 1995, the Honorary Curator of Micromounts at the Denver Museum of Science, Arnold Hampson, 2012, of Cortez who donated his micromount collection to the Colorado School of Mines, and Carolyn and Steve Weinberger, 2014.  For years Carolyn served as the Editor of the American Federation Newsletter and was a tremendous help during my year of writing land conservation articles for the Newsletter. Steve served as the Central Office of the Federation.

At the recent meeting two gentlemen were inducted into the Micromounters Hall of Fame: Michael Seeds, an astronomer at Franklin and Marshall College, and Renado Pagano, a collector from Milano?, Italy.  Dr. Seeds is a well known astronomer with numerous publications who entered mineral collecting later in life (he was not a career mineralogist). Pagono is an industrialist, and in conjunction with his spouse, have amassed a systematic and aesthetic collection of over 13,000 minerals.  Both presented the key talks at the Symposium, Seeds on the relationship of minerals and “stars,” and Pagano on sulfur in Sicily.  I learned much from both including Pagano’s note that mineral collectors often collect other items (see my last Post, October 7, 2020).

Bright orange desautelsite crystals scattered on serpentine matrix with bright white artinite.  I am uncertain about the different crystals on the left third of the photomicrograph.  Perhaps they are dehydrated desautelsite, or a different mineral. Width FOV ~6 mm.

  

A druse of nice, bright orange crystals of desautelsite.  Width FOV ~4 mm.

In 1979 the carbonate mineral desautelsite [Mg₆Mn₂(OH)₁₆[CO₃]-4H₂O] was named to honor Paul Desautels.  It is a rare, bright orange mineral associated with fractures and cracks in rocks called serpentinite.  These metamorphic rocks are composed of one or more mineral members of the Serpentine Group, magnesium silicates formed by hydration and metamorphism of mantle rocks along boundaries of tectonic plates.  Several other secondary magnesium minerals are usually associated with desautelsite, including artinite [Mg₂(CO₃)(OH)₂-3H₂O)], and hydromagnesite [(Mg₅(CO₃)₄(OH)₂-4H₂O] although desautelsite is the last mineral to form in the fractures.

Desautelsite is a very soft mineral (2 on Mohs) with translucent pseudo- hexagonal crystals forming an orange, druse-like, scaly crust.  Without a powerful microscope the individual crystals are exceedingly difficult to observe.

The type locality for desautelsite is in Lancaster County, Pennsylvania, and is associated with serpentinites. However, it is best known from two sites in California, especially the Artinite Pit in San Benito County. MinDat notes that at this locality an open cut of serpentinized rocks are exposed.  Secondary minerals like desautelsite grow on the altered surfaces of the spaces between the breccia blocks.  Other than these localities in Pennsylvania and California there is one locality in Maryland, and three in Japan, where the mineral occurs with other ultramafic rocks.  So, it is a rare mineral.

BTW, I missed out again.  On the NASDAQ Board Zoom Video Communications was trading at ~$62 on November 1, 2019 and ~$492 on October 9, 2020!  I also missed out on Apple! And Microsoft!

I think the one thing about the Zoom calls is unlike being in a room with people where you can look away or drift off, I feel like with Zoom, everyone's face is just dead center, head on, there is no drifting. It takes a lot of energy from me.            Mellody Hopson

WOW DINOSAURS AND THE UNITED STATES POSTAL SERVICE

 

All of science can be divided into physics and stamp-collecting.    Lord Kelvin

I am not a philatelist, a serious stamp collector, but as a kid I collected stamps as a fun hobby (along with coins, minerals, bird feathers,and numerous other objects).  A philatelist is a person like Art Ackley who bought his first stamp album when he was 8 and collected until his death (2019) at 95.  He also sold rocks and minerals at his shop on Stone Street in Colorado Springs for 45 years (see Posting May 24, 2020).  I collected stamps because of their geographic connotation and always had an atlas around to locate countries that produced the stamps—I learned much. In retrospect, I note that many of my stamps came from countries that were colonial in nature and governed by European rulers, for example French Equatorial Africa.  Today these colonies have different names as French Equatorial Africa is now the countries of Chad, the Central African Republic, the Republic of the Congo, and Gabon.  I suppose that rockhounds collecting stamps is not unusual and at one time the American Federation of Mineralogical Societies had a Commemorative Stamp Committee to encourage the publication of mineral-themed stamps by the USPS.

 

 The Kingdom of Yugoslavia (Kraljevina Jugoslavija) was established in 1929 and lasted until World War II when it was replaced by the Socialist Federal Republic of Yugoslavia (Socijalistička Federativna Republika Jugoslavija).  The breakup of the Republic started in 2003 and by 2006 Yugoslavia did not exist and was divided into 6 different countries: Serbia, Montenegro, Bosnia and Herzegovina, Croatia, North Macedonia, and Slovenia. I collected these stamps in the1950s.   

 

I had numerous, several pages, of German stamps in my collection.  I suspect they were printed pre1945 since Adolph Hitler is on one stamp (left side, fourth row). 

In 2019 the USPS produced a T.rex (Tyrannosaurus rex) series of four different stamps best sold in panes of 16.  These are beautiful, large, glossy, colored stamps showing different poses of the mighty dinosaur: 1) A face-to-face encounter with a T. rex approaching through a forest clearing; 2) a newly hatched T. rex covered with downy feathers; 3) a juvenile T. rex pursuing a primitive mammal; and 4) young adult T. rex with a young Triceratops. “The Nation’s T. rex,” the young adult depicted on two of the stamps, was discovered on federal land in Montana and is one of the most studied and important specimens ever found. Its remains are now exhibited at the Smithsonian Institution’s National Museum of Natural History in Washington, DC. Art director Greg Breeding designed the stamps with original artwork by scientist and paleoartist Julius T. Csotonyi (info from USPS).

The T.rex stamps have a lenticular component on two stamps that simulates motion. Several images are divided into thin, alternating parallel lines and overlaid with a transparent ridged plastic that alters a viewer’s perception of the scene when the stamp is rotated slightly—sort of like a hologram.  One animated stamp stimulates a face-to-face encounter with a charging T. rex. A second stamp shows a young adult and a juvenile Triceratops in both fleshed out and fossil forms.  You really need to buy at least four stamps to observe this neat effect.

The T.rex stamp set is the latest U.S. issue to celebrate prehistoric animals and fossils. The first U.S. issue was the 6¢ Age of Reptiles stamp, part of the 1970 Natural History pane of four (Bald Eagle, African Elephant, Haida Ceremonial Canoe, Apatosaurus in the swamp) issued to commemorate the 100th anniversary of the American Museum of Natural History in New York City.  The second was the wildly popular 1997 pane of 15 Jurassic and Cretaceous dinosaur 32¢ stamps.  Paleoartist James Gurney painted the original dinosaur panoramas for the panes: 1) A scene in Montana, 75 million years ago; and 2) A scene in Colorado, 150 million years ago. My framed pane was a Christmas present 23 years ago. A 33¢ T. rex stamp was issued in 2000 to celebrate the movie Jurassic Park.  And now in 2019, the innovative T.rex pane.  Thank you, United States Postal Service. 

 

Notice the following T.rex stamps on left side and in the middle--there are two different views.  Pane courtesy of the USPS.

I've been standin' here waitin' Ms Postperson

So patiently, for just a card, or just a letter

        As sort of crooned by the Marvelettes

DENVER FALL 2020 SHOW BY A NOSEHAIR

The 2020 Colorado Mineral and Fossil Fall Show is now over, and I am uncertain when I might be able to attend another show.  Perhaps in November at the Jefferson County Fairgrounds (Denver), perhaps even as late as February 2021 in Tucson.  I talked to several Tucson dealers in Denver and all believed that “Tucson of some sort” will occur.  Perhaps the “main show” will change but the ancillary shows scattered around city will be open for business--with or without the numerous international dealers. So I will continue with what I am doing, reading, playing with minerals, learning about new “things” (still working on those pesky boron minerals), keeping up with the yard work, keeping track of my grandchildren, staying away from crowds of people, and worrying about the future of our country.  The latter task seems to take up much or my time.

Do not watch the clock. Do what it does. Keep going.   Sam Levenson

Nodule with calcite crystals with three groups of pyrite.  Length of nodule ~5 cm.

Penetration twinning of calcite cubes.  Width FOV ~1.1 cm.

I did pick up a few interesting minerals at the Denver Show, not really any showstoppers, but minerals that attracted my attention—I liked them, and the prices were quite reasonable.  I mean one specimen is pyrite on calcite—what is so exceptional about that?  For one thing, my goal of being a lifelong learner just jumped up a notch or two as I spent several hours each evening learning about Friar Tuck and his friends!  How could that happen with some pyrite on calcite?  Well, now that you asked, the specimen was collected from Vale Road Quarry, Mansfield Woodhouse, Nottinghamshire, England, UK.  OK, I vaguely remember Nottinghamshire (Notts for short) from my youthful days of reading about Sherwood Forest, the Sherriff, and Robin Hood. Today the County brands themselves as the “motherland of the spirited outlaw” and large numbers of tourists visit the City of Nottingham, although the size of the city and its metro area (1,610,000) would not be familiar to the Sherriff.  Sherwood Forest still contains the Major Oak, known throughout the literary world as the provider of shelter and sleeping quarters for Hood's group of “Merry Men.”  I am not quite certain where Maid Marian stayed.

The Major Oak in Sherwood Forest   Photo Public Domain courtesy of XXLRAY.

For over a century, roughly mid-1800s to mid-1900s, Nottinghamshire was home to a thriving coal mining industry for there is 900-1000 feet of Carboniferous (Pennsylvanian Period of the U.S.) coal in the subsurface.  The large-scale mines were developed in the 1800s although there is evidence that shallow seams were mined during the Roman Conquest period (43-410 AD).  I could not locate much information about why the mining stopped other than production cost and pollution.  The final piece of coal mined in Notts reached the surface in 2015.

The Silverhill Colliery (a coal mine and its connected buildings) was a large coal producer and after closure there was a complete reclamation of the area. The land was turned into a county park with the spoil pile becoming an artificial hill that holds a stature of a coal miner and was declared as the highest point in the county.  A couple of years later some climbing enthusiasts used “extremely precise measurement” to decide if a nearby lane was actually higher that Silverhill.  As reported in the Nottinhampost.com the result was the lane was higher by a nose hair.  Can any reader think of a better way to forget about Covid, for a moment or two, than reflect on a contest that was won by a “nose hair?” 

Besides nose hairs, Nottingham has a great literary heritage, among others it is home to Lord Bryon and D. H. Lawrence.  Not bad!  

The Geding Coal Pit opened in 1899 and closed in 1991. 128 men died at the colliery, which produced over a million tonnes of coal per year in the 1960s. Courtesy Nottinghampost.com.

A coal colliery in Nottinghamshire before collapse of the coal economy and the reclamation of the mine and site.

I also note that almost all the coal mines have been, or are being, reclaimed and put into the public domain as parks or housing. Does this action say something about our nation’s policy of cutting off the tops of mountains and filling the valleys with debris in order to mine the coal?  The Pandemic makes be crabby.

Silverhill is an artificial hill in Nottinghamshire, and is one of the highest points in the county. Originally it was a mine spoil heap on the site of the former Silverhill colliery which closed in the1990s. It was subsequently landscaped by the Nottinghamshire County Council. Public Domain photo courtesy Alan Heardman. 

The miner is holding a Davy Lamp, a safety lamp for use in flammable atmospheres, invented in 1815 by Sir Humphry Davy. It consists of a wick lamp with the flame enclosed inside a mesh screen. It was created for use in coal mines, to reduce the danger of explosions due to the presence of methane and other flammable gases. Info and photo courtesy of mining-memorabilia.co.uk 

Nottinghamshire also has several other quarries than those associated with coal.  Most of these quarries, such as the Vale Road Quarry, are near the settlement of Mansfield Woodhouse where Permian age (on top of the Coal measures) sandstones and “magnesium limestones” (dolomite) crop out.  In 1304 the Church of St Edmund was built with local stone (magnesium limestone) and is still standing.  In 1839 the designer of the Houses of Parliament, Sir Charles Barry, selected a sand-colored magnesian limestone (Cadeby Formation) quarried from the Mansfield Woodhouse area as the foundation stone that would be used in its construction. Perhaps some of the quarried stone came from the location of my pyrite-calcite crystals.  I just don’t know.  What I do know is that the Vale Road Quarry has been repurposed (love that word) and is now (I believe after reading Council Meeting minutes)) a landfill.

A former magnesium limestone quarry near Mansfield Woodhouse. Photographer unknown.

The Woodhouse Warbler is a free, local community newspaper in the Mansfield Woodhouse area that was a joy to peruse (remember lifelong learning), and in fact, is an amazing piece of work run by volunteers over the last 20 years.  In sorting through the Warbler letters and recorded memories I found out that many of the local quarries had been repurposed due to drowning of local inhabitants.  Seems as if the abandoned quarry waters attracted the kids of the region for swimming and floating around on homemade rafts.  The January 2010 issue had much information on these abandoned quarries: 1) I was born and lived on Laburnum Grove just over the railway lines from Rouses quarry. There was a pump house there as there was a spring constantly filling the quarry with water. We played on rafts with oil drums underneath. But tragically a boy, who I think was a member of the Fells family drowned in there.; 2) We played in the water filled quarry just beyond the railway bridge on Common Lane in the 60’s a school boy from my old school (St Edmund’s Junior) was drowned there about that time, he got trapped under a raft.; 3) The quarries in the Woodhouse area, on Grant Piercy’s site for Stuffywood Hall he has info on Parliament Quarry on Vale Rd. with an 1861 Geology report for all the Mansfield area quarries. 3)  My great Grandfather Ashley operated Parliament Quarry on Vale Rd (now the Council depot) around the time of WW1 ; 4) and saving the best for last, I bumped into Jimmy Andrews coming out of the Quarry, clothes torn and when I asked him what his trouble was, ” I fell in the Crusher”. Rouses again. Jimmy’s dad Snotty Bob was the watchman. Can you just picture a man by the name of Snotty Bob?

Cinderhill Colliery 1920.  Photo courtesy of pictures of the past.org.uki

Church of St Edmund, Mansfield Woodhouse constructed in 1304 from magnesium limestone quarried locally. Photo Public Domain courtesy of Enchufla Con Clave.

Spodumene is a lithium mineral [LiAlSi₂O₈] that is usually associated with lithium-rich pegmatites and associated with lepidolite, tourmaline, quartz, various feldspars, and beryl. I am most familiar with spodumene found in pegmatites in the Black Hills of South Dakota. One of the most spectacular mines in the Black Hills is the Etta Mine near Keystone, now in private hands and probably off limits to collectors.  The Etta, originally a mica mine in a pegmatite, has produced monster crystals of spodumene, a lithium aluminum silicate. Hess (1939) noted that huge crystals of spodumene are mixed at every possible angle like toothpicks in a translucent gel (quartz).  In 1904, a crystal 42 feet long and 3 feet by 6 feet in cross section was found...The crystal weighed about 65 tons.  How would you like to find space for that crystal in your collection?  It should also be noted that spodumene is the source of three gemstones—kunzite, hiddenite, and colorless/clear (sometimes called triphane although the name is not in common usage).  Kunzite is pink to lilac in color due to small amounts of manganese.  Hiddenite, perhaps best known from the mines in North Carolina, is the emerald green variety with the color coming from chromium.  Triphane, the colorless to pale yellow variety, receives any color from iron.  Roberts and Rapp (1965) reported all three gems from pegmatites in the Hills.

Giant spodumene crystals in the wall of the Etta Mine near Keystone, SD.  Note miner for scale.  Photo taken in 1904 and courtesy of W.T Schaller and the U. S. Geological Survey archives

At the Show I picked up a specimen of pink spodumene, the variety kunzite, collected at the Dara-i-Pech Field, Konar Province, Afghanistan.  It is light pink in color (no irradiation), is not terminated nor gemmy but does have several nice striated crystal faces.  For any mineral collected from Afghanistan, I think of the hard work and dangers of the intenerate miners along with the smugglers transporting the treasures overland by mule (at least that was the story provided by a collector/seller in Tucson). The four bucks I paid seemed cheap. On the other hand, “UNDP’s National Human Development Report 2020 on minerals extraction in Afghanistan states that the country’s minerals extraction is poorly regulated, often illegal, and in many parts of the country is controlled by political elites, and by insurgents.”  Did I buy a “blood kunzite”?

Spodumene, variety kunzite, width of crystal ~1.5 cm.

MinDat noted that specimens labelled as coming from Dara-i-Pech do not necessarily come from this pegmatite field but may originate from any place in the Pech valley. So, the specimen is from Afghanistan.

Prehnite is a common mineral, a calcium alumosilicate [Ca₂Al₂Si₃O₁₀(OH)₂], found in metamorphic rocks (prehnite-pumpellyite facies) or more commonly in vugs of basaltic igneous rocks associated with zeolite minerals.  These vug fillings are the result of circulating hydrothermal fluids depositing various minerals.  I am most familiar with the prehnite found in the Triassic basalts filling the half-grabens in New Jersey (see posting Oct. 21, 2019).

Spheres of green prehnite with very dark green prismatic epidote crystals.  Width mineral FOV ~3.3 cm. 

Most prehnite is easy to identify as specimens are some shade of green or yellow-green and have a globular, reniform, or stalactitic morphology.  However, there are colorless, gray, or white specimens and some are granular or compact masses.  All have a white streak, sort of a subvitreous luster, a hardness of 6+ (Mohs), and rather invisible individual crystals.  Once you see prehnite, you will usually recognize it forever.

The prehnite I brought home from the Show is associated with dark green, prismatic crystals of epidote[{Ca₂}{Al₂Fe}(Si₂O₇)(SiO₄)(OH)], a common mineral found mostly in metamorphic rocks but also in some granites.  The crystals are often striated, often twinned, hard at 6-7 (Mohs), a vitreous to resinous luster, a gray to white streak, and ranges from transparent to opaque.  It usually occurs in some shade of green, especially pistachio green or yellow green.  However, a greater amount of iron can cause crystals to become almost black and increase the specific gravity.

Prehnite and epidote occur together as secondary minerals in metabasalts—igneous basalts that have been subjected to circulating hydrothermal solutions and heated.  My specimen was collected at a well-known locality, near the village of Sandare in Mali.  Most specimens on the market are marked as collected in Sandare; however, that village is merely the colleting point for miners bringing in the specimens.  If you are not familiar with the Republic of Mali, it is a landlocked nation in northwestern Africa southeast of Algeria and includes parts of the Sahara Desert.  It is the 8^th largest country in Africa and is the third largest producer of gold in Africa (much by itinerant miners).

This final specimen brought home from Denver is a rock composed of grossular crystals [Ca3Al₂(SiO₄)₃], a type of garnet.  Now, grossular is a quite common mineral and forms nice hard (6.5-7.5 Mohs), vitreous, dodecahedral and trapezohedral crystals.  The crystals are brown and translucent-transparent in my specimen although they also occur in a variety of other colors: green (color of gooseberries, Ribes grossularium), emerald green (tsavorite), yellow, red, red-orange (hessonite), white, red, and orange. Specimens have a high specific gravity and therefore are “heavy.”

Crystals of vitreous grossular.  Width FOV ~1.2 cm. 

Crystals of grossular with a hard, white, massive (not very diagnostic) material (not calcareous) that the specimen label notes is clinohumite, a pinkish colored variety of zoisite.  However, I cannot observe any pink shade in the mass.  I do note that several claims in the area are mapped as "unnamed thulite claim."

The specimen came from the Bird Springs Garnet Claim (Nelson Range Deposit) Lee Mining District, Inyo County, California.  I could not locate much information about the claim except that it is a skarn deposit near the summit of the Nelson Range in wilderness land managed by Death Valley National Park.  The best known minerals from Bird Springs are clusters of amethyst-tipped quartz crystals with Japan Law twinning (at one time in the collection of Rock Currier as observed on MinDat). 

Skarns are coarse grained metamorphic rocks rich in calc-silicate minerals and members of the Garnet Group that are formed when hydrothermal fluids, often generated from nearby granite plutons (or metamorphic rocks), interact with other sedimentary or igneous rocks.  The classical skarns are when the fluids intrude the carbonates dolomite or limestone.  I have been unable to locate much information about the geology of the Nelson Range, located on the western side of Death Valley.

Hikers report evidence of numerous mining activities in the Nelson Range although I cannot locate production numbers.  The highest peak in the Nelson Range is unofficially termed Galena Peak indicating the presence of lead.  Near the Bird Springs Garnet Claim there are a number of other small claims and diggings that indicate wollastonite, thulite (zoisite), zeolites, copper, and lead (the Cerussite Mine).  The latter shows “mineralization in a vein deposit with a 2 to 8-inch-wide seam of oxidized lead and silver ore hosted in a limestone” (MinDat.org).

So, that is my report about some of the minerals I snagged at the Denver Fall Show.  I have a few more that might show up in a future posting.  Right now, I am thinking about a small sign on my desk: I was born to be wild…but only until 9pm or so.  

REFERENCES CITED

Hess, F. L., 1939, Lithium: United States Department of Interior, Bureau of Mines, IC 7054. 

Roberts, W. L. and G. Rapp Jr., 1965, Mineralogy of the Black Hills: South Dakota School of Mines Bulletin 18.