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November-December 2012

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Mineral Mysteries: Curved, Bent, and Twisted Crystals

Crystals that are bent, twisted, or curved are often encountered in nature. These may come in a variety of forms. We probably all are familiar with gwindel quartzes (figs. 1), crystals that are characterized by being flattened, are usually smoky in color, and appear to be twisted about a vertical axis, the a-axis, according to Frondel (1962). For this reason they are commonly referred to as twisted quartz. The name gwindel is an obscure German word for “twisted”; it's so obscure, in fact, that it doesn't even appear in my German dictionary.

John S. White, a consulting editor of Rocks & Minerals, operates Kustos, a museum/collector consulting business. Now retired, he is the former curator-in-charge of the National Mineral and Gem Collection at the Smithsonian Institution.

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