Crystalline versions of Gypsum are collectively known as Selenite.

Chemical Formula: CaSO4·2H2O
Class: Sulfates Calcium
Hardness: 2
Coloration: Colorless, white, light brown to yellow or pink

How to identify it/Unique Characteristics or Properties: Gypsum is extremely common but can come in many different forms and looks. A very fine grained version is alabaster, while the various crystalline versions (collectively known as selenite) can come in everything from large single crystals to “Desert Roses” that closely resemble flowers of stone. The color can also change of the crystalline forms depending on impurities contained in the crystals.

Where to it find in…

The Northwest: Numerous places, very common mineral
Other: Gypsum is extremely common, found all over the world, most famously in France, Carlsbad Caverns, White Sands NM, the Great Salt Plains, etc.
Past Uses: A key ingredient in Plaster of Paris, used for carvings, as mortar, adhesive, and as a binding agent in paints.
How it was Made: Evaporation of ocean brine, leaving behind minerals.
Interesting Facts: This is the second softest mineral and can be scratched with almost anything.