HISTORY, NAME, LOCALITIES: Gypsum, pronounced JIP-sum, is hydrous calcium sulfate. Its name stems from the Greek gypsos, or “plaster,” alluding to one of its early uses. Selenite, pronounced SELL-en-ite, is the crystalline variety of gypsum. Its name is derived from the Greek selénités, literally “stone of the moon” (from seléné, or “moon”), referring to the moon-like, pearly luster of its cleavage surfaces. Collecting localities are found in Canada, Peru, Mexico, Spain, and the United States (Oklahoma, Utah, New York, Tennessee, and Nevada).
MINERALOGY, PROPERTIES, OCCURRENCE: The selenite variety of gypsum [hydrous calcium sulfate, CaSO4•2H2O] crystallizes in the monoclinic system as prismatic or bladed crystals with distinct rhombic form, and as arrowhead-shaped twins with beveled edges. Pure selenite is colorless or white, but impurities create a range of pale grays, yellows, reds, and browns. Selenite is transparent to translucent with a hardness of 1.5-2.0, perfect cleavage in one direction, vitreous to pearly luster, and a specific gravity of 2.3-2.4. It occurs mainly in chemical-sedimentary, marine-evaporite formations of sandstone, limestone, or rock salt.
METAPHYSICAL PROPERTIES, LORE, USES: Selenite, along with other forms of gypsum, is used in plaster, soil conditioners, paint fillers, cement retardants, and drywall products. According to modern metaphysical practitioners, selenite conveys white light that calms troubled minds, stabilizes emotions, and clarifies thoughts.
COLLECTORS’ INFORMATION: The most collectible selenite crystals have water-clear transparency, a range of pale colors, and well-developed, rhombic crystals.