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May-June 2013

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Collector's Note: Unusual Fluorites from Inner Mongolia

Recently, several samples of what appear to be garnet crystals (originally presumed to be grossular-andradite) from Inner Mongolia have been analyzed and shown to be fluorite. The samples are striking in their visual similarity to garnet and are thus worth noting. The sample reported here is a well-formed dodecahedral crystal, 2.5 cm across, embedded in a matrix of a gray asbestiform mineral (fig. 1). The fluorite is highly gemmy with very minor inclusions of individual fibers of the matrix material. It exhibits no internal cleavage planes, and the crystal faces show pronounced stepped surface mounds (hillocks) that are elongate in the [110] directions. The color is a honey-brown similar to that of many topazolite variety andradites. The crystal and matrix are reminiscent of some topazolite specimens from the Malenco Valley, Lombardy, Italy.

Dr. John Rakovan, an executive editor of Rocks & Minerals, is a professor of mineralogy and geochemistry at Miami University in Oxford, Ohio.

James W. Spann and his wife, Gail, are collectors of fine minerals from worldwide localities, with a strong interest in geochemistry and its effect on diversity, color, and form.

Jeff Fast is a longtime mineral collector and dealer based in Connecticut.

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