Diamond
The slightly uneven eight-sided 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.
General
Category	minerals
Formula (repeating unit)	C
Strunz classification	01.CB.10a
Identification
Molecular mass	Lua error in Module:Convert at line 669: attempt to index field 'per_unit_fixups' (a nil value).
Color	Typically yellow, brown or gray to colorless. Less often blue, green, black, translucent white, pink, violet, orange, purple and red.
Crystal habit	Octahedral
Crystal system	Isometric-Hexoctahedral (Cubic)
Twinning	Spinel law common (yielding "macle")
Cleavage	111 (perfect in four directions)
Fracture	Conchoidal (shell-like)
Mohs scale hardness	10 (defining mineral)
Luster	Adamantine
Streak	Colorless
Specific gravity	3.52±0.01
Density	3.5–3.53 g/cm3
Polish luster	Adamantine
Optical properties	Isotropic
Refractive index	2.418 (at 500 nm)
Melting point	Pressure dependent

A diamond (from the ancient Greek αδάμας – adámas "unbreakable") is a re-arrangement of carbon atoms (those are called allotropes).

Diamonds have the highest hardness of any bulk (all one type) material. Because of this, many important industries use diamonds as tools for cutting and polishing things. Many of them are clear, but some of them have colors, like yellow, red, blue, green and pink. Diamonds of a different color are called "fancies".