Selenite crystals 2 to 6 inches in length have recently been found in a few places around the shores of Great Salt Lake in the soft sodium clays of the lake bottom. This occurrence may be significant in explaining the origin of selenite crystals in shales, so commonly seen on the erosion surfaces of shale formations in arid regions. Since the lake waters are impoverished in calcium ions, the selenite crystals have never been precipitated in historical times and are not believed to be a precipitate from the lake waters in times past. Bacteria may be the cause of a steady state in the clays conducive to the growth of the gypsum crystals, and physical changes incident to the consolidation of the clays may also be significant.
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