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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').
Selenium is toxic in high concentrations. As sodium selenite, the chronic toxic dose for human beings was described as about 2.4 to 3 milligrams of selenium per day. [7] In 2000, the US Institute of Medicine set the adult Tolerable upper intake levels (UL) for selenium from all sources - food, drinking water and dietary supplements - at 400 μg/day. [8]
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".
Demesmaekerite is a rare uranium selenite mineral with the chemical formula: Pb 2 Cu 5 (UO 2) 2 (SeO 3) 6 (OH) 6 ·2H 2 O. . It is named after the Belgian mineralogist Gaston Demesmaeker, who worked at the Musonoi Mine in Katanga.
Iron(III) selenite is an inorganic compound with the chemical formula Fe 2 (SeO 3) 3. It exists anhydrous form and as various hydrates. It exists anhydrous form and as various hydrates. The heptahydrate is produced by the reaction of ferric chloride and selenous acid (or sodium selenite ) at a pH of 1.05. [ 3 ]
In mineralogy, crystal habit is the characteristic external shape of an individual crystal or aggregate of crystals. The habit of a crystal is dependent on its crystallographic form and growth conditions, which generally creates irregularities due to limited space in the crystallizing medium (commonly in rocks ).