June 05, 2007

Rare gem triplite specimen discovered in Tucson.

by David Weinberg

Sharp mineral dealer discovers extremely rare mineral specimen being used as a paper weight at the Tucson show.

Last year, while exploring some remote corner of the Tucson Gem and Mineral Show, Denver based gem and mineral dealer Morgan Sonsthagen came across an attractive bright pinkish-orange rock being used as a paper weight. Thinking it was a rhodochrosite he asked the dealer, "how much for that rock on the pile of papers"? The seller claimed that he couldn't sell the rock because it was holding down all of his papers. After a short negotiation, Morgan volunteered to find the guy a new rock for his pile of papers and they agreed on a price for the orange rock.

That 150 gram rock turned out to be triplite, an extremely rare mineral found sparingly at a few localities throughout the world. Morgan suspects that the material is the same as the material from Guilin, China, incorrectly identified as triploidite in Gems and Gemology (summer 2006). Apparently, the only other gem quality pieces come from Pakistan near Dassu and most of those are somewhat brownish in color. Very few if any other triplites are available in the bright orangey colors of Morgan´s material and nearly every other triplite deposit only produces grainy granular opaque material.

The rough was processed in Bangkok by Warren Weise at his Thonburi factory. In addition to some smaller stones, two large gems were recovered; a 21.29 ct. pear shape and an 11.05ct. round. Some of the stones were tested at the AIGS gem lab by Dr. Laurent Massi and some of the rough was donated to the RRUFF University of Arizona Mineralogical project for further analysis.

Triplite is a rare fluoro-hydroxide phosphate mineral that forms in phosphate rich granitic pegmatites and high temperature hydrothermal veins. With formula (Mn,Fe2+)₂(PO₄)(F,OH), calcium and magnesium commonly substitute in the divalent cation site. In color and appearance, triplite can be very similar to rhodocrosite, another manganese bearing mineral and it is most likely the high concentration of manganese that is responsible for the bright peachy color. Chemically, triplite is also quite similar to triploidite the difference being that triplite is F dominant while triploidite is OH dominant.

Triplite was first described in 1813 for an occurrence in Chanteloube, Limousin, France. The name is derived from the Greek triplos for triple, in reference to the three cleavage directions. Other occurrences include the Shigar Valley, Pakistan; China; Bavaria, Germany; Kimito, Finland; Karibib, Namibia; and Maine, Connecticut, Arizona and Colorado in the United States. Triplite is quite rare and difficult to facet do to its brittleness and cleavage. Only a few cut stones have been reported and all of them are from the Shigar Valley in Pakistan. One specimen from Dudley Blauwet was loaned to the GIA for examination. General absorption to 450nm, weak absorption bands at 470nm and 490nm, and a stronger band at 520 - 620nm were observed with a desk model spectroscope. Microscopic inspection revealed finger print type and two phase inclusions.

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Related links

• Triplite classification from the Multicolour Library
• An extensive selection of Triplite´s in a variety shapes, sizes, and price ranges.
• The RRUFF Project.