DENVER SPRING SHOW WITH EOSPHORITE & COLLINSITE

He meant the Grand Canyon was only a mood of nature, a bold promise, a beautiful record. He meant that mountains had sifted away in its dust, yet the canyon was young. Man was nothing, so let him be humble. This cataclysm of the earth, this playground of a river was not inscrutable; it was only inevitable—as inevitable as nature herself. Millions of years in the bygone ages it had lain serene under a half moon; it would bask silent under a rayless sun, in the onward edge of time.    Zane Grey

On the way home from the Tucson Re Do I stopped in to ogle at a really magnificent, awe inspiring, deep canyon!    

21-23 May 2021 Denver Colorado Mineral and Fossil Spring Show

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.

A substantial number of dealers were present but I don't have the exact count--more than 50 but less than a hundred  I would guess! It seemed to me that: 1) loose cabs and some faceted stones were abundant; 2) mineral specimens and crystals were less common and scarce and those present were the common types; 3: jewelry with nice gemstones was rather rare although bead necklaces were common.  With those observations in mind I would say that the show was geared towards: 1) the general public (non rockhounds); and lapidaries looking for raw specimens.  Whatever the case, I enjoyed the displays and hope the show was successful.  And, I did come home with a few treasures!

The main hall for the dealers had plenty of room.  In addition there was a smaller space for wholesale dealers.

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Signs that warm my heart: $5 minerals and 50% off!

What would a rock and mineral show be without Brazilian amethyst geodes? However, the big towers were lacking.

A few fossils were found but mostly of the common varieties.

Donald K. Olson had some nice minerals, especially sulfur crystals.

A well curated collection collection of Phil Persson (Persson Fine Minerals) out of Denver.

Show staples---beads and bead necklaces.

New Era Gems had a great display of gemmy tanzanite; some treated to deepen color, some natural.

Dennis Beals of Denver displays at numerous show across the country.

One of the interesting specimens I picked up at the Show was collinsite with eosphorite collected from Lavra da Ilha, near Taquaral, Minas Gerais, Brazil, and ex Alfred Stevenson collection.  Two things about this statement: 1) I did not recognize the collector, Alfred Stevenson.  However, I did find that Mr. Stevenson was born in 1916 and died in 2007 in New York and was an active rockhounder.  Evidently Mr. Stevenson amassed a large collection since his specimens have been, or are, for sale via a wide variety of mineral auctions. 2) I did not recognize the Brazilian collecting locality (not surprising) but did find a really interesting group of mineral articles in the Free Library (see References Cited).  In one article Guido Steger said this about the locality:  When in Brazil I often ask hopefully about the possibility of specimens from the Lavra da Ilha, near Taquaral. In the early 1970's, wonderful specimens of rose quartz crystals from Lavra da Ilha created a sensation. The coxcomb-like arrangement of the crystals, combined with their pale to deep rose-pink color, makes these unusual specimens very appealing. In some cases a white or clear quartz crystal is garlanded by the rose quartz crystals. Two commonly associated species are eosphorite-childrenite, in well-formed, transparent crystal aggregates…

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.

Different camera angles of above spray.

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