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Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks. Deposits are known to occur in strata from as far back as the Archaean eon. [16] Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins.
The main sources of calcium sulfate are naturally occurring gypsum and anhydrite, which occur at many locations worldwide as evaporites. These may be extracted by open-cast quarrying or by deep mining. World production of natural gypsum is around 127 million tonnes per annum. [17]
A gypsum block is made of gypsum plaster and water. The manufacturing process [1] is automated at production plants where raw gypsum (CaSO 4 ·2H 2 O) is ground and dried, then heated to remove three-quarters of the bound water and thus transformed into calcium sulfate hemihydrate (CaSO 4 ·½H 2 O), also known as gypsum plaster, stucco, calcined gypsum or plaster of Paris.
Selenitic lime, also known as Scotts' cement after Henry Young Darracott Scott, is a cement of grey chalk or similar lime, such as in the Lias Group, with about 5% added gypsum plaster (calcined gypsum). [13] Selenite is a type of gypsum, but selenitic cement may be made using any form of sulfate or sulfuric acid. [18]
Gypsum materials consist of calcium sulfate dihydrate (CaSO 4 ·2H 2 O). Sulfate-reducing bacteria convert sulfates to toxic hydrogen sulphide gas; they are killed by exposure to air, but the moist, airless, carbon-containing environment in a landfill is a good habitat for them.
Gypsum concrete is a building material used as a floor underlayment used in wood-frame and concrete construction for fire ratings, sound reduction, radiant heating, and floor leveling. [1] It is a mixture of gypsum plaster, Portland cement , and sand .
This list of mines in Indonesia is subsidiary to the list of mines article and lists working, defunct and future mines in the country and is organised by the primary mineral output. For practical purposes stone, marble and other quarries may be included in this list.
Cultural properties of Indonesia are those items defined by Indonesian law as of "important value for history, science, and culture", and include both man-made artefacts and natural objects. [1] The cultural properties number more than 8,000 and include ancient Hindu and Buddhist temples , mosques , historic colonial buildings , forts , art ...