n. A saline evaporite consisting of anhydrous calcium sulfate (gypsum).
the GNU version of the Collaborative International Dictionary of English
n. A mineral of a white or a slightly bluish color, usually massive. It is anhydrous sulphate of lime, and differs from gypsum in not containing water (whence the name).
The Century Dictionary and Cyclopedia
n. Anhydrous sulphate of calcium.
Word Usage
"It is frequently associated with minor quantities of anhydrite, which is calcium sulphate without water, and under the proper natural conditions either of these materials may be changed into the other."