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March-April 2012

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A Re-discovered Twin Law in Kyanite from Africa

At the 2009 Tucson Gem and Mineral Show examples of kyanite from Nani, Loliondo, Arusha Region, Tanzania, were first observed by one of the authors (JSW). One dealer had several trays of mostly broken pieces in small sizes. These were for the most part cleavages with no terminations and few crystal faces. What was most eye-catching about this kyanite was the color. We are accustomed to seeing blue to white and sometimes green kyanite but this rich orange—almost golden—color was stunning. The fact that it is found in the same deposits that have been producing similarly colored, large euhedral spessartine crystals for some years somehow made seeing kyanite in this color not too surprising.

The vast majority of the lots at that Tucson Show consisted of small linear crystal fragments, much longer than they were wide. Many had gemmy portions suitable for faceting into very small stones, 1 carat or less in size. Among these were a number of what appeared to be V-shaped twinned pieces, and two of them were purchased for this reason. At the time the buyer (JSW) assumed that such twinning for kyanite was well established in the literature, so it was with considerable surprise that we learned later that this was not the case.

R. Peter Richards, a consulting editor of Rocks & Minerals, focuses his mineral collecting activities on intersting crystal habits, twinned crystals, and epitactic relationships.

John S. White, a consulting editor of Rocks & Minerals, operates Kustos, a museum/collector consulting business. The mineral whiteite was named in his honor, and he was the recipient of the 2010 Salotti Mineralogical Award.

Dr. Peter B. Leavens is emeritus professor of mineralogy at the University of Delaware, where he taught mineralogy and geology for thirty-eight years. He was also curator of the university's Mineralogical Museum (udel.edu/museums) for twenty-five years.

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