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Graphite
Graphite
is carbon. It is also known as black lead or plumbago. It is a very soft to steel-grey mineral
having a greasy feel. Its hardness is between 1 and 2 and the specific gravity varies from 2
to 2.3. The lustre of graphite varies from metallic to earthy and its streak is black.
Graphite is
used in the manufacture of pencils, refractory crucibles, paints etc. |
| Orpiment
Orpiment is a trisulphide
of arsenic. Crystals are rare. Hardness varies from 1.5 to 2 and the specific gravity is 3.5.
The colour of orpiment is of various shades of yellow. Its lustre is resinous.
Orpiment usually
associated with realgar. Orpiment is used as a pigment. |
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Wolframite
Wolframite is a
tungstate of iron and manganese crystallising in the monoclinic system. Crystals are commonly
tabular or prismatic. It is a heavy mineral with a specific gravity of 7 to 7.5 and hardness
of 5 to 5.5. It is dark brown or black in colour. Its streak is black and its lustre is
sub-metallic.
Wolframite is
used as an ore of tungsten. |
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Mineralogy