Satin Spar variety Selenite is a type of Gypsum found in Morocco. The term Satin Spar refers to one of several formations in which Selenite can form, this one acts as a natural fiber optic and illuminates with the smallest hint of light. Satin spar refers to these characteristics - it is most often silky, fibrous, and translucent (pearly, milky).
The origin of the word "selenite" is through Middle English selinete, from Latin selenites, from Greek selēnitēs (lithos), literally, moonstone or stone of the moon, from selēnē (Moon). The ancients had a belief that certain transparent crystals waxed and waned with the moon.
All varieties of gypsum are very soft minerals (hardness: 2 on Mohs Scale). Gypsum has natural thermal insulating properties, all varieties feel warm to the touch.