Gypsum is a very soft mineral composed of Calcium Sulphate Dihydrate, with the chemical formula CaSO4�·2H2O. It has colourless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. It may also occur silky and fibrous, and is called satin spar. Gypsum is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. The crystals can also be quite large. Gypsum is a natural insulator, feeling warm to the touch when compared to a more ordinary rock or quartz crystal. Plaster of Paris is made by heating gypsum to about 300 degrees Fahrenheit, driving 75% of the water out of the mineral. Hardness is 2 and can be scratched by a fingernail. Specific Gravity is approximately 2.3+ (light)