When I saw the headline shown above I started doing cartwheels, well not really gymnastic cartwheels but a little fast shuffle. Was it really true? Were the rock and mineral shows coming back on line? I had just attended a couple of days of a shortened show schedule in Tucson, the April Re Do (see previous postings), but was delighted to see that an event was slated close to Colorado Springs. Furthermore, our local rock and mineral club, CSMS, rescheduled their annual show from June to October. Things were looking up. The 2021 Rocky Mountain Federation event in Las Vegas was postponed until 2022; however, the Sublette County Rockhounds in Big Piney, Wyoming, jumped in and volunteered to host the 2021 RMFMS and the American Federation meeting and shows June 16-20. I expect a large crowd as rockhounds want to escape to the country.
But back to the Denver Show. This event was sponsored by a private promoter (RMAG Promotions) and is not to be confused with the annual fall showcase sponsored by a consortium of local Denver area rock and mineral clubs. The event was held at the Crowne Plaza Denver Airport Convention Center. A really good couple of points: parking was free and space inside the center was more than adequate. A not so good point: I-70 and I-35 are still undergoing major construction and traffic was fouled.
The main hall for the dealers had plenty of room. In addition there was a smaller space for wholesale dealers.
A well curated collection collection of Phil Persson (Persson Fine Minerals) out of Denver.
Show staples---beads and bead necklaces.
The locality is on a little island in the Jequitinhonha River which is
flooded most of the time. When the water is low--only a few weeks out of the
year--the digging site is exposed, and then the owner can try to extract the
elusive rose quartz crystals, which are rare and are highly valued as
gemstones.
Unfortunately major finds had grown rare by the early 1980's, and top-quality
specimens almost vanished from the market. The island may be reached from
Taquaral, a very small village between Itaobim and Aracuai, in Minas Gerais.
Eosphorite
is a member of my favorite group, the phosphates (containing the PO4 Ion—a central phosphorous atom
surrounded in a tetrahedral arrangement by 4 oxygen atoms), that often seem to turn up at rock and
mineral shows and immediately attract my attention. The mineral is a hydrous manganese aluminum
phosphate [MnAl(PO4)(OH)2-H2O) that forms
long, more stout than slender, prismatic crystals that usually appear as
radiating clusters. Crystals are usually some shade of brown in color but are
sometimes pink or reddish. They are
“shiny” on the surface but somewhat less than vitreous—a subvitreous luster on
the exterior. Broken crystals often have
a vitreous light amber color on the interior.
Depending on the color, crystals range from transparent to
translucent. They leave a white streak
and have a measured hardness of ~5.0 (Mohs).
In my specimen most crystals show a wedge shape termination.
Spray of eosphorite crystals; width of spray ~1.0 cm.
Scattered eosphorite scattered and embedded in collinsite.
Eosphorite is in a solid solution series with childrenite where iron (Fe++) substitutes for the manganese (and many writers use eosphorite-childrenite for specimen ID). I don’t believe there are formal “middle members” of the series and eosphorite is Monoclinic while childrenite is Orthorhombic (Crystal Systems).
Eosphorite
is associated with other secondary phosphates in granite pegmatites, often
lithium-rich forms, where primary phosphate minerals are available as
precursors for the colorful secondary forms.
The famous Tip Top Mine in Custer County, South Dakota (Black Hills) has
both eosphorite and collinsite present.
Speaking
of collinsite, the second group of crystals on my specimen is labeled as such;
however, I am somewhat bothered by the fact that the single photo in MinDat
from the Brazilian locality does not “look much like” my specimen. But….the morphological descriptions of
collinsite, and the photos from the Tip Top Mine and the Rapid Creek area in
the Yukon, Canada, seem to match this specimen.
I need to have Tom Loomis up at Dakota Matrix take a peek.
White to yellow while crystals of collinsite (with scattered brown eosphorite crystals). Width pf photomicrographs ~1.0 cm).
Collinsite
is a hydrated calcium magnesium phosphate [Ca2Mg(PO4)2-H2O]
that is often brown in color but can range to colorless, black, white, pale
blue or yellowish white. It is
translucent with a white streak and a hardness (Mohs) of 3.0+. It has a silky luster and crystals are commonly
bladed to prismatic (at times globular masses or fibrous). Superficially it reminds me of fairfieldite
(hydrated calcium manganese phosphate—see Posting Dec. 14, 2020) in
which it forms a solid solution series.
In other words, it looks like many other secondary phosphates. Like most of these minerals it is a secondary
weathering product with a primary phosphate precursor(s).
So,
this has been a quick summary of the 2021 Denver Spring Show. It was an enjoyable day in which
to look at minerals and talk to the dealers. I look
forward to the summer shows.
REFERENCES CITED
Guido
Steger Memoirs of a mineral
collector--Part 2: fifty-nine treasure hunts in Minas Gerais, 1969-2005..
(n.d.) >The Free Library. (2014). Retrieved Jun 29 2021 from https://www.thefreelibrary.com/Memoirs+of+a+mineral+collector--Part+2%3a+fifty-nine+treasure+hunts+in...-a0147065816
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