An
elongated, flattened crystal of Diamond in a matrix of Kimberlite, from South
Africa.
CHEMISTRY C Carbon
CRYSTALLOGRAPHY Isometric (Cubic)
CRYSTAL GROWTH AND HABITS Most crystals of Diamond are modified octahedrons but they are also found as dodecahedral, tetrahedral or cubic crystals. Diamond crystals are commonly flattened or elongated and are also found as crude spheres with a radial structure.
COLOR AND OTHER OPTICAL PROPERTIES Diamonds are colorless, pale yellow to deep yellow, brown or bluish. Other colors of diamond are also known. Diamond is transparent to translucent and even opaque, depending on the amount of impurities (commonly graphite).
HARDNESS 10
SPECIFIC GRAVITY 3.5
LUSTER Adamantine to greasy
STREAK White
BREAKABILITY Diamond has a very good octahedral cleavage (4 directions) and also has conchoidal fracture and is brittle.
OCCURRENCE Diamonds are formed in high temperature, high pressure environments as in igneous kimberlite pipes or dikes. Diamonds are also found as placer deposits.
ASSOCIATED MINERALS Olivine, Phlogopite, Pyrope, Diopside, Ilmenite