Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco3). The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 470°c, and vaterite is even less stable.
The term plaster can refer to plaster of paris (also known as gypsum plaster), lime plaster, or cement plaster. This article deals mainly with plaster of paris / gypsum plaster.
Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O.
Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: caco3). The deposition of limestone strata is often a by-product and indicator of biological activity in the geologic record.
Phosphogypsum refers to the gypsum formed as a by-product of processing phosphate ore into fertilizer with sulfuric acid. Phosphogypsum is radioactive due to the presence of naturally occurring uranium and radium in the phosphate ore.