ANS:B - gypsum

Plaster of Paris. Mid-15c, originally it was made from the extensive gypsum deposits of Montmartre in Paris. Any of a group of gypsum cements, essentially hemihydrated calcium sulfate, a white powder that forms a paste when mixed with water and hardens into a solid, used in making casts and molds. Plaster of Paris is made by heating the mineral gypsum. When gypsum is heated to about 150° C it losses water and produces the powder, plaster of Paris. Hemihydrate Calcium Sulfate (2CaSO4. H2O) is commonly known as plaster of Paris. It is formed by heating gypsum. Gypsum plaster, or plaster of paris, is produced by heating gypsum to about 300 degrees F (150 Degrees C)