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.