Gypsum is a naturally occurring mineral in many parts of the United States and the world.
The chemical name of gypsum is calcium sulfate dihydrate.
The chemical formula for pure gypsum is Ca(SO4)•2(H2O).
In the chemically pure form, gypsum contains 23.28% calcium (Ca) and 18.62% sulfur (S) in the readily available sulfate form (SO4).
However, the typical gypsum sources that are commercially available for agricultural often contain impurities which result in a Ca level between 18%-23% Ca and 15%-19%. Gypsum is also available as a byproduct material.