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.
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Dunkleosteus
shull.
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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.
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Trilobite: $500.
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Nice brittle stars!
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Nice crinoid slab.
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Trilobites and brittle stars. What are the chances?
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Wow. Big
teeth.
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| Crocodilian object d’art. |
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Very interesting.
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Spheres anyone?
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The palm frond fell in with the fish.
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Ammonite object d’art with added copper.
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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.
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Nodule of yellow crandallite with a few “white” eyes
of wardite. Width ~ 6.5 cm.
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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.