Gypsum is named from Greek "gypsos" - plaster, alluding to its practical use. It has been known from antiquity.
Gypsum is composed of hydrated calcium sulphate and takes many forms, occurring as tabular, bladed and diamond shaped crystals. it also occurs in fibrous form, and in compact, granular masses, and as rosette shaped aggregates with included grains of sand.
Gypsum varies from colourless to white, gray, yellowish, reddish, greenish, and brown.
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. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.
Gypsum has several variety names that are widely used.
Selenite is the colourless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the greek for Moon and means moon rock.
Another variety is a compact fibrous aggregate called Satin Spar. This variety has a very satin like look that gives a play of light up and down the fibrous crystals.
A fine grained massive material is called Alabaster and is an ornamental stone used in fine carvings for centuries, even eons.
Desert rose is the colloquial name given to rosette formations of the minerals gypsum and barite with sand inclusions. The 'petals' are crystals flattened on the c crystallographic axis, fanning open along characteristic gypsum cleavage planes.
Crystals of gypsum can be colourless and transparent, making a strong contrast to the most common usage in drywall. 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. Sheets of clear crystals can be easily peeled from a larger specimen.