Selenite is the clear, crystalline variety of the mineral Gypsum. It is a hydrous calcium sulfate, holding two waters in its molecular structure. The selenite deposits that have captured everyone’s attention during this current time are the fantastic cathedral like chambers discovered in the Naica Mining District in Chihuahua, Mexico, and featured in the Smithsonian Magazine, and National Geographic. These hot, extremly humid underground caves formed selenite crystals that grew up to 50 feet long.I remember looking at a cut section of pipe from the Naica district that had interlocked, spearlike crystals of selenite within the interior, formed from the pumping of solutions.
Selenite derives its name from the ancient Greek word for “moon stone”, in reference to its icy, moonlight look. Scott’s Rock & Gem periodically offers sheets of clear selenite from Mojave county, Arizona. This is a prolific locality with loads of material and I put some photos of the pit in my Trona 2010 blog. I’ll post more info about the locality here, just as soon as I can, but if I don’t do it fast enough and you want to go digging, just email me for directions. I’ll be glad to send them over. Happy Rockhounding!