Graphite

Formula: C native element
Specific gravity: 2.09 to 2.23
Hardness: 1 to 2
Streak: Black to steel-grey
Colour: Black to steel-grey
Solubility: Insoluble in hydrochloric, sulphuric and nitric acid
Environments:

Pegmatites
Metamorphic environments (typical)
Hydrothermal environments

Graphite most commonly occurs in metamorphic environments, where it may form a considerable proportion of the rock. In these cases, it has probably been derived from carbonaceous material of organic origin that has been converted into graphite during metamorphism. It can also be found in veins and in pegmatites.
It is a mineral of the greenschist, amphibolite and granulite facies.
Graphite is a common constituent of phyllite, and it also may be found in limestone, schist and gneiss.
Graphite is the low pressure, high temperature polymorph of diamond. At 200oC graphite is the stable polymorph at pressures up to about 20 kbar (SERC).

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