gypsum - pink rock gypsum from the Pliocene Quartermaster Formation, Armstrong County, Texas - unit of five student specimens
gypsum CaSO4 ･ 2H2O
Pink rock gypsum from the Pliocene Quartermaster Formation, Palo Duro Canyon, Armstrong County, Texas.
Gypsum is primarily formed as a chemical precipitation in an evaporative environment. This gypsum was deposited in shallow evaporative flats during a series of Pliocene marine transgressions and regressions - times of alternating rise and fall of sea level. It is interbedded with the siltstones and mudstones of the Quartermaster Formation.
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