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Selenite (mineral)
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<p>Selenite, satin spar, <a href="/facts/Desert_rose_(crystal)/3rSSNjEV">desert rose</a>, and gypsum flower are <a href="/facts/Crystal_habit/x2S1HVVY">crystal habit</a> varieties of the mineral <a href="/facts/Gypsum/MItYU70n">gypsum</a>. </p><p>All varieties of gypsum, including selenite and <a href="/facts/Alabaster/wLAtReg3">alabaster</a>, are composed of <a href="/facts/Calcium_sulfate/mTD8oGaH">calcium sulfate</a> dihydrate (meaning that it has two molecules of water), with the chemical formula CaSO4·2H2O. Selenite contains no <a href="/facts/Selenium/k975NApC">selenium</a>, the similar names both derive from <a href="/facts/Ancient_Greek/LIK7NlUh">Greek</a> <i>selḗnē</i> (σελήνη '<a href="/facts/Moon/zKHqEMPb">Moon</a>'). </p><p>Some of the largest crystals ever found are of selenite, the largest specimen found in the <a href="/facts/Naica_Mine/oYr4mPnq">Naica Mine</a>'s <a href="/facts/Cave_of_the_Crystals/PIsI0tKT">Cave of the Crystals</a> being 12 meters long and weighing 12 tons. </p>