Plaster of paris

http://global.britannica.com/EBchecked/topic/463673/plaster-of-paris

plaster of paris, quick-setting gypsum plaster consisting of a fine, white powder, calcium sulfate hemihydrate (see calcium), which hardens when moistened and allowed to dry. Plaster of paris is prepared by heating calcium sulfate dihydrate, or gypsum, to 120°–180° C (248°–356° F). With an additive to retard the set, it is called wall, or hard-wall, plaster.

Used since ancient times, plaster of paris is so called because gypsum was early used near Paris to make plaster and cement. Plaster of paris is also used to precast and hold parts of ornamental plasterwork placed on ceilings and cornices and is used in medicine ... (100 of 171 words)

http://www.omnia.co.za/pebble.asp?relid=1140

https://www.gypsum.org/about/gypsum-101/what-is-gypsum/ One hundred pounds of gypsum rock contains approximately 21 pounds (or 10 quarts) of chemically combined water. Gypsum rock is mined or quarried, crushed and ground into a fine powder. In a process called calcining, the powder is heating to approximately 350 degrees F, driving off three fourths of the chemically combined water. The calcined gypsum, or hemihydrate, becomes the base for gypsum plaster, gypsum board and other gypsum products.

http://www.omnia.co.za/pebble.asp?relid=1140 The plant, designed with an annual capacity of approximately 210 000 tons, was launched following a R35m total investment. The plant’s location at Phokeng, just outside Rustenburg gives it vital proximity to much of South Africa’s cement manufacturing capacity. In line with the Omnia Group’s commitment to the environment and sustainable development, the plant will process an existing stockpile, which is a by product of the phosphoric acid plant, resulting in the rehabilitation of the surrounding area once the stockpile is exhausted. The plant will treat the gypsum, enabling the gypsum’s use by customers manufacturing cement and cement board, including Lafarge Cement, Lafarge’s Board Division, and Holcim, Protea Chemical’s original technology partners on the plant. Gypsum is a crucial ingredient in cement manufacture, as it acts as a retarder, delaying the time it takes for cement to set

see http://www.proteachemicals.co.za