Formula: C native element
Specific gravity: 3.5 to 3.53
Colour: Colourless, yellow, green, pink, blue, black
Solubility: Insoluble in hydrochloric, sulphuric and nitric acid
Plutonic igneous environments
Most commonly diamond is found as placers
in alluvial deposits where it accumulates because of its inert chemical nature, its great hardness
(it is the hardest natural substance known) and its fairly high
specific gravity. The rock in which it is found in situ is
It is formed deep in the mantle, and is only brought
to the surface via kimberlite pipes. It is also found in alluvial deposits, along with
corundum and zircon.
pressure the diamonds dissolve back into the rock. To occur and survive in a metastable
state at the surface they must arrive from depth quickly.
Diamond may be found in kimberlite, and also occasionally in eclogite.
Diamond is the high pressure polymorph of graphite. At 800oC diamond is the stable polymorph at pressures above about 35 kbar (SERC).
Coexistence of diamond and carbonate minerals:
The coexistence of diamond and carbonate minerals in mantle eclogite is explained by the reaction:
dolomite + coesite → diopside + diamond + oxygen
MgCa(CO3)2 + 2SiO2 → CaMgSi2O6 + 2C + 2O2
Back to Minerals