from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A colorless, white, gray, blue, or lilac mineral of anhydrous calcium sulfate, CaSO4, occurring as layers in gypsum deposits.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A saline evaporite consisting of anhydrous calcium sulfate (gypsum).
from 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).
from The Century Dictionary and Cyclopedia
- n. Anhydrous sulphate of calcium.
The name anhydrite was given by A.G. Werner in 1804, because of the absence of water, as contrasted with the presence of water in gypsum.
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.
A geochemical process called anhydrite swelling has been confirmed as the cause of these uplifts.
Other important types of minerals include: the carbonates (e.g. calcite, CaCO3) the sulfides (e.g. galena, PbS) and the sulfates (e.g. anhydrite, CaSO4).
A secondary, and minor source, of raw calcium sulfate is the mineral anhydrite.
Gypsum and anhydrite are abundant and minor amounts of salt, potash and limestone occur.
The third series describes receipt of pure boron through action on boron anhydrite by magnesium:
During the period from 1860 to 1985, sulphuric anhydrite emissions, one of the leading causes of acid rain, increased from seven million tons to approximately 155 million tons annually.
Further heating of gypsum, slightly beyond 200° C (not achieved by solar energy) produces anhydrite gypsum (CaSO4), which when mixed with water, sets very slowly.
Thus the sulphate constitutes the minerals anhydrite, alabaster, gypsum, and selenite; the carbonate occurs dissolved in most natural waters and as the minerals chalk, marble, calcite, aragonite; also in the double carbonates such as dolomite, bromlite, barytocalcite; the fluoride as fluorspar; the fluophosphate constitutes the mineral apatite; while all the more important mineral silicates contain a proportion of this element.