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Chalcopyrite
Chalcopyrite or copper pyrites is a
sulphide of copper and iron crystallising in the tetragonal system. It commonly occurs in
massive form. Its hardness varies from 3.5 to 4.3. It is brass yellow in colour and its streak
is greenish black. Chalcopyrite is distinguished from pyrite by its low hardness and brass
yellow colour.
In India, Chalcopyrite is being mined in the Singhbhum district of
Bihar.
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Garnet
Garnet form a group
of complex silicate minerals, all of which crystallise in the cubic system.
Their hardness varies from 6.5.to
7.5 and their specific gravity ranges from 3.15 to 4.3. They occur in a variety of colours and
produce a white streak.
Garnets commonly occur in igneous
and metamorphic rocks.
When transparent, garnets are used
as gem stones, they are used as an abrasive when they are non-transparent.
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Bauxite
Bauxite
is a hydrous oxide of aluminium and is the only ore from which aluminium is extracted. When
pure it is white in colour. Commonly it is yellow, brown or red or a mixture of these
colours. Its hardness is variable and the specific gravity is 2.5.
Bauxite is
formed by prolonged weathering of aluminium bearing rocks under tropical climatic
conditions. In Tamilnadu, bauxite occurs at Shevaroy hills, Yercaud in Salem
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Magnesite
Magnesite is a carbonate of
magnesium. It is white, light grey, yellow in colour and breaks with a flat concoidal
fracture. Its hardness ranges from 3.5 to 4.5 and the specific gravity varies from 2.8 to 3.
It effervesces with acids.
Magnesite is chiefly
used in the manufacture of refractory bricks and crucibles.
In Tamilnadu , high grade magnesite occurs at Chalk Hills, Salem
district. In Karnataka State, it occurs in the districts of Hassan and Mysore. |
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Mineralogy