M840 - Selenite Crystals (Utah).

Selenite is a gypsum material used as a plaster and in cement. Selenite is a Hydrous calcium sulfate. Hardness 1-1/2 to 2. Can be scratched with your fingernail. Gypsum is a very common sulfate mineral. Although it may be found in several rock types, it develops principally in sedimentary rocks of chemical origin, where it forms rock gypsum deposits in the beds that may be up to 30 feet in thickness. It also occurs associated with dolomite and barite in hydrothermal replacement deposits.

From  Utah.

Price:   $ 2.50 each