PYROPHYLLITE: TUCSON GEM SHOW REPORTS: MINERS CO-OP

My next daily journey took me to the Miners Co-op Rock Show, a venue now in its second year.  Many of the Co-op vendors were once at the Kino venue; however, the Kino soccer fields are now off limits to sellers and many migrated to this new area.  I enjoy the Miners Co-op since it is the “genuine thing” of small-time vendors selling from tents and pickup beds or piles emplaced on tarps with their small camping trailers circling the area.  A tamale vendor wanders through the tents around lunch time and an older model pickup drives around selling water from a large tank in the bed.  Mom and pop operations at their finest.  In addition, I recognized some of the vendors as members of the Colorado Springs Mineralogical Society, while others were from nearby towns.

The tents often were not large enough to cover the specimens on the tables from the massive weekend rains.

Large specimens were often just placed on large plastic tarps.

I love the mixture of minerals, jewelry, used lapidary equipment, and whatever “for sale” at a variety of venues.  Note the straw placed around the booths after the recent rains.

I really do not like to observe the sale of Native American artifacts like there pot shards. 

My “$5 or less” mineral of the day is pyrophyllite, actually a “real buy” at $1.  I have sort of been fascinated by this aluminum silicate hydroxide [Al₂(Si₄O₁₀)(OH)₂] since first observing the radiating masses coming out of Graves Mountain, Georgia.  Although the best collectable specimens are these aggregates of radiating needles, pyrophyllite also occurs as massive grains and folliated laminar masses.  The silicate layers give it a nice cleavage.  It is a very soft mineral, ~1.5-2.0 (Mohs), with a pearly luster, somewhat transparent in the non-massive form, and found in a variety of earth-tone colors: brown, green, gray-white, brown-yellow, gray. 

Radiating silver-brown rosettes of pyrophyllite from Graves Mountain, Lincoln County, Georgia.  Width ~4.5 cm.

Pyrophyllite is isomorphous with talc and almost has identical physical properties; both are monoclinic, however, talc has magnesium substituting for the aluminum.

Pyrophyllite may be found in a few hydrothermal rocks; however, most occurrences are in low grade metamorphic rocks where it usually is an alteration product of kyanite [Al₂SiO₅].  The Graves Mountain specimens are especially attractive stellate aggregates.

CRANDALLITE: TUCSON GEM SHOW REPORTS & PALEO

Tuesday in Tucson was a paleontological day—more of a viewing day.  I collected thousands of vertebrate fossils over my career in academe and all were added to museum collections as most were taken from federal lands with permits.  Almost all were very small mammals or reptiles that could fit in small vials and your front shirt pocket—I was not a collector of dinosaurs or large marine reptiles.  At one time I collected some large musk oxen and a few other things; however, that seemed like a heavy lifting task, especially when digging and plastering were involved.  But today, I still enjoy looking at some of these fantastic specimens.

 

Dunkleosteus shull.

There are tens of thousands of Moroccan invertebrate fossils on the Tucson marketplace including trilobites and cephalopods by the truck load.  However, I often am quite confused about the authenticity of many of these specimens!  Many seem “to good to be true,” for example when starfish are plopped in the middle of a slab of trilobites, or when every appendage detail is visible on a trilobite.  Perhaps all is well and I am a pessimist.  However, I would certainly not pay some rather high prices without a detailed examination under magnification.

 

Trilobite: $500.

Nice brittle stars!

Nice crinoid slab.

Trilobites and brittle stars.  What are the chances?

Wow.  Big teeth.

Crocodilian object d’art.

Very interesting.

Spheres anyone?

The palm frond fell in with the fish.

Ammonite object d’art with added copper.

I noticed that many of the large vertebrate fossils contained an appreciable amount of “plaster” (or some more advanced filler).  That fact is not readily disclosed by many sellers.  I would liken these products to some of the gem sales---respectable dealers will disclose if a particular gem is synthetic, oiled, filled with glass paste, or a variety of other sorts of things.  Or, is it “buyers beware?”  There is nothing wrong with plaster/filler if such details are disclosed.

What about my $5 or less mineral of the day?  I am fascinated by the arsenates, phosphates and vanadates and especially those collected from some of my favorite states—like Utah.  So, I was quite pleased to pick up a partial nodule of crandallite. 

Nodule of yellow crandallite with a few “white” eyes of wardite.  Width ~ 6.5 cm.

Crandallite is a rather uncommon hydrated calcium aluminum phosphate [CaAl₃(PO₄)₂(OH)₅-2H₂O] that often is associated with the phosphates variscite and wardite.  I suppose that when most rockhounds think about collectable and colorful crandallite and variscite, the Little Green Monster Mine in Utah County, Utah, pops up, along with the names Ed Over and Art Montgomery.  Over was a mineral collector from Colorado Springs and teamed with college professor (Lafayette College) and mineral dealer Art Montgomery.  Together in a few short years the dynamic duo brought to market and museums pounds/tons of spectacular mineral specimens including topaz from Pikes Peak, red wulfenite from the Red Cloud Mine in Arizona, various minerals from the high altitude Mt. Antero, Colorado, green epidote from Prince of Wales Island in Alaska, and the variscite from Fairfield, Utah (near the south end of the Oquirrh Mountains).  They worked the Little Green Monster Mine for a few short years in the late 1930s and brought out the colorful phosphate nodules by wheelbarrows.  Today the mine is closed and all Little Green Monster Mine specimens are decades old and many are really quite expensive (four to five figures).  My specimen seemed like a real bargain!

Variscite [AlPO₄-2H₂O] is the original phosphate and forms in dense microcrystalline nodules with trace amounts of chromium and phosphorous imparting the green color.  Crandallite seems the first alteration mineral to form as variscite picks up and adds calcium from solution.  Normally colorless, trace iron gives the Utah crandallite a yellow color.  Numerous other exotic phosphates such as wardite, englishite, gordonite, millisite, montgomeryite and overite are also present at the Little Green Monster.