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As the gypsum directly enters into chemical reaction, the higher
the percentage of CaSO4.2H2O content in gypsum
the better is the plant performance and the greater is the production
of ammonium sulphate.
the Middle Ages, zircon was believed to contain remedial power,
protecting the wearer from diseases and banishing insomnia. The name "zircon"
is believed to have derived from the Arabic words, "zar",
meaning gold, and "gun", meaning color. It was discovered in
Germany in 1789 by Martin Klaproth.
Thailand and Cambodia are the world's major suppliers of zircon with
large deposits near the border of the two countries. Vietnam, Burma,
Sri Lanka and Africa also provide a large supply of these marvelous
gemstones to the world market.
the sulphate of calcium with two molecules of water, CaSO4
is one of the most important industrial minerals in India. Three
varieties of gypsum are known namely:
is crystalline. It is transparent to tanslucent. Massive variety is
known as alabaster and fibrous or silky variety as satinspar, both
pure white to dull white in colour unless otherwise tingled due to
impurities. Commercial deposits are mostly found as marine beds.
Gypsum is classed under minerals of evaporite group, though vein
deposits and massive deposits in the limestone country formed due to
interaction of limestone with sulphurous water are not uncommon.
Bedded deposits are found associated with anhydrite (CaSo4
anhydrous gypsum), limestone, shale and clay. Gypsum beds are devoid
of fossils. The origin of gypsum has been a subject of great interest
in the past and continues to be a research problem for geologists
|2 and can be
scratched by a fingernail
colorless or gray, but can also be shades of red, brown and yellow
||thin crystals are
flexible but not elastic, meaning they can be bent but will not bend
back on their own. Also some samples are fluorescent. Gypsum has a
very low thermal conductivity (hence it's use in drywall as an
insulating filler). A crystal of Gypsum will feel noticeably warmer
than a like crystal of quartz
||vitreous to pearly
especially on cleavage surfaces
flexible crystals, cleavage and hardness
Gypsum is chiefly utilized in the manufacture of ammonium sulphate
, plaster of
Paris, distemper and cement. A considerable quantity of gypsum is used
as manure. It is a good soil conditioner and gives growth of peas,
beans and alfalfa. Gypsum and anhydrite can be a good source of
sulphur. Anhydrite has been utilized in the UK and West Germany for
the extraction of sulphur. The use of gypsum for the manufacture of
gypsum-stucco for making tiles, roof planks and board products is fast
increasing in USA. Stucco is the industrial name for the product
obtained from the calcination of gypsum to hemihydrate stage.
Gypsum has the very useful property of becoming plastic like mass
when heated upto 175ºC. At this temperature it loses about 3/4th
of the water molecules. The product thus obtained is known as plaster
of Paris. It can be mixed with water, spread and cast into different
forms and sizes. It can be mixed with expanded perlite and vermiculite
and made into wall plaster and castings.
The silica (SiO2
) and sodium chloride (NaCl), should not
be more than 6% and 0.01% respectively, and it should be free from
clayey meterial. As the gypsum directly enters into chemical reaction,
the higher the percentage of CaSO4
content in gypsum the better is the plant performance and the greater
is the production of ammonium sulphate. Ammonium sulphate is
manufactured by reacting ammonium carbonate and powdered gypsum and
the calcium carbonate sludge thus recovered as a by-product is
utilized in the manufacture of cement. This is one of the greatest
advantages in utilizing gypsum for fertilizer manufacture.
Although gypsum of 75% to 85% purity is used in the manufacture of
cement, yet a minimum of 82% CaSO4
preferred. Nearly 0.04 to 0.05 tonne of gypsum is required per tonne
of cement produced. It is mixed with the clinker in the end and then
crushed to form cement. It acts as retarder in quick setting of
For the manufacture of Plaster of Paris, selenite crystals of purity
varying from 97 to 80% are preferred. Three grades of Plaster of Paris
are generally known and manufactured:
surgical grade the selenite should be of the highest purity. Other
grades are used for making dolls and castings in pottery industry.
Sometimes pure white lumpy gypsum of alabaster type is used for the
Plaster of Paris manufacture. For the manufacture of distemper also
pure white lumpy gypsum of high purity is required. Gypsum of 75%
purity and below is used as manure or as sweet-lime.
Gypsum is spread all over the world. It is extensively mined in
Europe, the UK, Russia, the USA, Canada and African and Asian
countries. In Asia, India is the largest producing country and
possesses extensive reserves which are available for export to Ceylon,
Japan and other far-east countries. At present Japan is getting
supplies of gypsum from Canada.
In the USA, gypsum is mined in many states, the important producing
states being California, Iowa, Michigan, Texas and New York. It is
found to occur in horizons from Silurian to Pliocene age.
Canadian deposits are found in British Columbia, Manitoba, New
Brunswick, Newfoundland, Nova Scotia and Ontario. The important
producing centres are Windemere, British Columbia; Gypsumville and
Amarnath, Manitoba; Havelock and Hillsborough, New Brunswick; Flat Bay
Station, Newfoundland; Millers Creek, Wentworth, Makay Settlement and
Nappan Little Narrows (Cape Breton Island), Cheverie, Milford and
Walton in Nova Scotia and Hagersville, Caledonia in Ontario. At
Milford, a gypsum bed, of some 135 metres thickness, underlain by
dolomite is found. Finely crystalline to selenitic type gypsum is
found. Gypsum is worked by quarrying except at Hillsborough, New
Brunswick where underground operation is resorted.
Abundant reserves of gypsum are found in Cyprus. It occurs in two
well-defined groups of deposits, one in a narrow arcuate zone which is
remarkably parallel to the trend of the Kyrenia range, in the north of
the island; this includes the important Lupatza gypsum outcrop and the
other occurs on the periphery of the Troodos igneous massif. Both
these deposits are of upper Miocene age.
The production comes principally from the northern area of Honshu.
There are about 30 mines with an average annual production of 8 lakh
tonnes. Domestic production is mainly utilized in the manufacture of
cement. Japan imports over a lakh tonnes of uncalcined gypsum per
year, mainly from the USA, Mexico and Australia.
In West Pakistan beds of gypsum along with anhydrite, occur in saline
series of salt range. The important deposits located in Jhelum
district are at Khewra gorge, Dandot, Chanuwla, Makrach, Dand Khel,
Mari Hill and Kalabagh Hill.
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