Selenite takes its name from the Greek word for the Moon, a nod to the cool, luminous glow that seems to move within its translucent blades. It grows where mineral-rich water evaporates and leaves behind gypsum, gathering into satin spar, desert rose, and fishtail forms. Long treated as a stone that sits between light and matter, it has been used for windows, meditation, and the clearing of space across many cultures.

Selenite is a transparent-to-translucent crystalline variety of gypsum, a hydrated calcium sulfate with the formula CaSO₄·2H₂O. It crystallizes in the monoclinic system and forms in evaporite deposits where mineral-laden water dries, producing satin spar (fibrous with a silky sheen), desert rose (bladed rosettes), and fishtail (twinned) habits. At a hardness of 2 on the Mohs scale it is very soft, easily marked by a fingernail, and it will slowly dissolve if left in water.

Named for Selene, the Greek goddess of the Moon, the stone was called selenites lithos, the moonstone, because its pale sheen was believed to wax and wane with the lunar cycle., The Romans cut translucent gypsum known as lapis specularis into thin panels and set it into windows, letting a soft, filtered light into homes and temples., and Folk tradition held that placing selenite in the corners of a dwelling wove a quiet shield of light around it, keeping unwanted influences from crossing the threshold.

I let selenite quiet the noise so my thoughts can settle; my mind is calm, my space is clear, and I can see the whole of my life with steady understanding.