KUTNOHORITE: TUCSON GEM SHOW REPORTS: KINO

"Big rocks" are still available for purchase at several Kino dealers.

The shows at Kino, the ex-Tucson Electric Park shows, have changed in the last couple of years.  At one time the venue was stacked with small dealers selling a wide variety of interesting rocks and minerals.  Most of these mom & pop dealers were set up on the soccer fields; however, the fields are now off limits and most of these small dealers have moved to the 22^nd Street venue.  The remaining dealers, and there are many, still peddle a wide variety of goods including Bob Marley reggae shirts, “Persian” rugs, welded steel animals and “big” rocks with quartz crystals or azurite.  There also are plenty of beads and amethyst cathedrals.  I am always amazed at how many tens/hundreds of thousands of beads are for sale each year in Tucson.

There are some decent vendors with minerals for sale but it seems that Deccan Plateau zeolites were the most common.  I was impressed with the numerous vendors selling lapidary supplies and equipment.  I am not interested in such, but the prices seemed decent.  One thing that I did miss was the “golf cart” hauling visitors from the parking lots to the show venues---it seemed to disappear this year.

 

Take your choice of beads at various prices and designs.

Large slabs of selenite gypsum quarried in Utah.

A "tent" full of vendors.

Several vendors had quality lapis for sale with accompanying high prices.

I did locate a small dealer from Kansas (my original home state) willing to “talk” minerals (and Jayhawks) and tried to convince him to bring his wares to the CSMS Show in June.  At any rate, he had a small selection of “half-price” specimens so I nabbed a couple.  One was a carbonate that was not in my vocabulary—Kutnohorite [Ca(Mn,Mg,Fe)(CO₃)₂].  Since the purchase I have been reading about it, and examining such under the scope.  It seems a fairly rare mineral, a calcium magnesium carbonate related to dolomite [CaMg(CO₃)₂], and in a series with ankerite [CaFe(CO₃)₂].

Photomicrographs of deep red, gemmy andradite (garnets) crystals with a druse of tiny crystals of bladed white-pink kutnohorite.   Lower left andradite crystal ~2 mm in width. The camera did not pick up the mineral colors.

Most of the time kutnohorite consists of aggregates of tiny bladed crystals that are brown to pale pink or pale white in color. The pink hue increases as the magnesium increases while iron imparts a light brown color. Most of the time the mineral is quite dull or earthy in luster, somewhat translucent, and has a hardness of ~3.5-4.0 (Mohs). When fractured, the end result is a number of tiny conchoidal pieces.

My specimen came from the N’Chwaning II Mine in the Kalahari Manganese Field, where the manganese deposits are in the Hotazel Formation of Proterozoic age (Precambrian).  This is largest land-based sedimentary manganese deposits in the world, perhaps covering ~425 sq. miles. The ore has been subjected to hydrothermal alteration (temperatures up to 450°C) and metamorphism and is rich in braunite, bixbyite, hausmannite, marokite and hematite together with minor amounts of calcite. Andradite and barite are common gangue minerals. Additional minor minerals include  tephroite and rhodochrosite as well as aegirine (http://wwwu.edu.uni-klu.ac.at).  The origin of the giant manganese deposits has been debated for many years. “Proposed models cover a diverse spectrum of genetic processes, from large-scale epigenetic replacement mechanisms, to submarine volcanogenic-exhalative activity, to purely chemical sedimentation whereby the influence of volcanism is of reduced significance” (Tsikos and Moore, 2006).

The Kalahari Manganese Field, Northern Cape Province, South Africa, is the world’s most prolific producer of manganese. This mining region has produced some of the world’s finest rhodochrosite and hematite, as well as the finest ettringite, sturmanite, olmiite, sugilite, inesite, hausmannite, and thaumasite. Two of these mines (Wessels and N’Chwaning II) are together type localities for 19 species, including diegogattaite, wesselsite, lavinskyite, manganvesuvianite, marshallsussmanite, and sturmanite (www.mineralspecies.com).

REFERENCES CITED

Tsikos, H. and J.M. Moore, 2006, The chemostratigraphy of a Paleoproterozoic MnF- BIF succession -the Voelwater Subgroup of the Transvaal Supergroup in Griqualand West, South Africa:  South African Journal of Geology, v. 109.

RUBY & SPINAL: TUCSON GEM SHOW REPORTS: 22nd STREET

The 22^nd Street Show consists of a very large tent-like structure that contains in excess of 100 individual vendors.  Most of these sellers have large “booths” containing several tables—more “big-time” vendors rather than “mom and pop” operations.  I spent nearly the entire day perusing rocks, minerals, fossils, beads, equipment, and a wide variety of “lots of things related to our hobby.”  I particularly enjoyed some fabulous dinosaur casts made available by Triebold Paleontology headquartered in Woodland Park, Colorado.  Triebold also operates a museum known as the Rocky Mountain Dinosaur Resource.  If readers might be traveling through Woodland Park, take a break and visit this nifty museum.

 

Triebold Paleontology: A "bone-headed" dinosaur.

Triebold Paleontology: White River Group mammals from the South Dakota (maybe Nebraska) badlands.

Triebold Paleontology: Daspletosaurus, a tyrannosaur collected from the Late Cretaceous Judith River Formation, Montana.

Ceratopsian dinosaur of Late Cretaceous age.  Note the horn and frill in the rear of skull.

Triebold Paleontology:  Saurodon, a fish collected from the Niobrara Formation (Chalk Beds), western Kansas.  Note the elongated predentary bone (lower jaw).

The 22^nd Street venue also holds some of the “stars” associated with the TV show The Prospectors.  Amanda and Travis Anderson had a quite large venue selling mostly Pikes Pikes and Mt. Antero specimens. The Busey family was present and Dwayne Hall. All seemed to be busy signing autographs on posters. 

Dwayne Hall of The Prospectors holds court.

Travis and Amanda Anderson and their booth; a wide variety of Pikes Peak minerals for sale.

A couple of other vendors had large displays of Green River, Wyoming, fish and some beautiful palm fronds.  There was a nice display (and sale) of Solenhofen (Germany) fossils.  Opal was in abundance and some of the cuts were really nice, but quite expensive.  Numerous jewelry vendors were up and running with prices ranging from $10 earrings or pendants to blue sapphire rings selling for five figures.  It was just a nice day wandering around and sometimes talking to friendly vendors.

These two skulls show a new use for Arkansas quartz crystals!

I ran onto a vendor selling specimens of red ruby and pink-red spinel and decided I really need one of each-$5 per specimen.  Their colors contrast nicely with the white marble matrix.  From what the vendor told me, all of his gems come from Pakistan in an area named the Hunza Valley The gem deposit are located in rocks (metamorphic ocean platform carbonates) that were modified when proto-India banged into the Asian continent during the Himalayan mountain building events.

A nice modified octahedron crystal of ruby from the Hunza Valley in Pakistan.  I could not pick up the correct color in this photomicrograph;  however, it is a nice "ruby red." Front width, across the base, is ~5 mm.

Photomicrograph of dark pink spinel em-placed in white marble with a smaller crystal of gold-brown phlogopite.  Width of larger crystal ~5 mm.

Photomicrograph, pink specimen of spinel.  Length (up-down) ~ 1 cm.

Photomicrograph, small crystal of spinel with faces while large specimen is "massive."  Length of small crystal ~2 mm.

A previous Blog (11/7/12) detailed information about ruby and spinel.

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.