Several varieties of gypsum exist. Selenite is the name given to clear, colorless crystals of gypsum.
Satin spar is the variety name for masses of extremely fine, needle-like, parallel gypsum crystals.
Solid masses of gypsum without discernable crystal structure are given the variety name alabaster . Gypsum is extremely soft and can be scratched with a fingernail. This makes the material very easy to carve. Gypsum pellets expand when water is applied. This makes gypsum good as an agricultural product for breaking up soil for planting.