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Gypsum is an abundant, naturally occurring mineral that is mined or quarried for a variety of uses - predominantly for the production of gypsum board and gypsum plaster. It is believed that the vast worldwide deposits of gypsum ore were formed by the precipitation of minerals and the evaporation of inland seas some 140 million years ago! Gypsum is also produced synthetically. One process uses the desulfurization of environmentally harmful flue gases at fossil-fuel burning power plants to create benign and beneficial gypsum. See information on byproduct gypsum.
Chemically, gypsum is know as hydrous calcium sulfate (CaSO4.2H2O). The two molecules of water are chemically bound to the crystal lattice during the crystallization process. One of the many unique properties of gypsum is the ability to release this water when heated (in a process called calcination) and recombine with the water to re-form gypsum. It is fascinating to realize that the steam plume from a gypsum board plant is water captured by the gypsum while dinosaurs roamed the earth! The presence of the two water molecules (accounting for approximately 21% of the minerals weight) and high insulative properties of the rock contribute to gypsum's use as a premier fire resistant material.
Gypsum plaster, easily dating to 2000 B.C., has been found in the Egyptian pyramids. The development of gypsum plaster as a modern building material dates back to around 1835 with more advances occurring in the late 1870's. Augustine Sackett is given credit for the invention of what we know today as gypsum board. Sackett's patent on plaster board or Sackett Board dates to 1894. |
