The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral. Its lustrous faces also indicate that this crystal is from a primary deposit.
|Crystal symmetry||Fd3m (No. 227)|
|Color||Typically yellow, brown, or gray to colorless. Less often blue, green, black, translucent white, pink, violet, orange, purple, and red.|
|Twinning||Spinel law common (yielding "macle")|
|Cleavage||111 (perfect in four directions)|
|Mohs scale hardness||10 (defining mineral)|
|Diaphaneity||Transparent to subtransparent to translucent|
|Refractive index||2.418 (at 500 nm)|
|Melting point||Pressure dependent|
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form, but diamond almost never converts to it. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are utilized in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.