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Gypsum occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses called selenite. Selenite contains no significant selenium; rather, both substances were named for the ancient Greek word for the Moon. Selenite may also occur in a silky, fibrous form, in which case it is commonly called "satin spar".
Selenite, satin spar, desert rose, and gypsum flower are crystal habit varieties of the mineral gypsum.. All varieties of gypsum, including selenite and alabaster, are composed of calcium sulfate dihydrate (meaning that it has two molecules of water), with the chemical formula CaSO 4 ·2H 2 O. Selenite contains no selenium, the similar names both derive from Greek selḗnē (σελήνη 'Moon').
Saharan gypsum desert rose from Tunisia (length 47 cm) Baryte rose from Cleveland County, Oklahoma (size: 10.2 × 7.1 × 5.5 cm) Large desert rose formation in the Tunisian desert A desert rose is an intricate rose -like formation of crystal clusters of gypsum or baryte , which include abundant sand grains. [ 1 ]
Selenite is a fibrous variety of gypsum, [1]: 527 the most common form of satin spars; Gypsum, satin spar [2]: 429 in the form of a lustrous fibrous variety, not, however, defined as selenite; [3]: 217 Calcite or calcite spar is a fibrous variety [2]: 429 superficially resembling selenite, [4]: 169 but much less common in nature;
Acicular colorless scolecite crystals in a group with pale green apophyllite and very light pink stilbite Gypsum (selenite variety): Santa Eulalia District, Chihuahua, Mexico Serandite clusters from Poudrette quarry, Mont Saint-Hilaire, Montérégie, Québec, Canada Botryoidal balls of shattuckite, from Otjikotu, Kaokoveld, Kunene, Namibia Ball ...
The gypsum is mostly in the form of alabaster. There are several types of alabaster found at the site, including pink, white, and the rare black alabaster. This black alabaster can be found in only three veins in the world, one each in Oklahoma, Italy and China. Another form of gypsum can be found in the many selenite crystal formations. [4]
Selenite "sword", 22.6 by 2.6 by 1.6 centimetres (8.90 in × 1.02 in × 0.63 in). A small version of the giant crystals, likely found in a natural cavity in the mine. A scientific team coordinated by Paolo Forti, specialist of cave minerals and crystallographer at the University of Bologna (Italy), explored the cave in detail in 2006.
A petrographic microscope, which is an optical microscope fitted with cross-polarizing lenses, a conoscopic lens, and compensators (plates of anisotropic materials; gypsum plates and quartz wedges are common), for crystallographic analysis. Optical mineralogy is the study of minerals and rocks by measuring their optical properties.