Diamond

Diamond is a native element mineral, pure crystalline carbon (C), whose atoms lock into a rigid cubic lattice that makes it the hardest known natural material. Diamond crystallizes from carbon at extreme pressures (50,000+ atmospheres) and temperatures (1,000-1,300 degrees Celsius) found 150-200 kilometers below Earth's surface, deep in the upper mantle. These conditions exist beneath ancient continental cratons - the oldest, thickest, most stable portions of continental crust.

Diamonds reach the surface through rare, explosive volcanic eruptions called kimberlite and lamproite eruptions. These eruptions originate deep in the mantle and travel upward at speeds exceeding the speed of sound, carrying diamond-bearing rock to the surface in pipe-shaped volcanic structures. The speed matters - slow ascent would allow diamonds to convert to graphite (the stable form of carbon at surface conditions).

Most diamonds are between 1 and 3.5 billion years old. They formed in the Archean and Proterozoic eons, long before complex life existed. Some diamonds contain inclusions of minerals that no longer exist anywhere else accessible on Earth, making them time capsules preserving evidence of ancient mantle chemistry.

Diamond is identified by its supreme hardness (10 - nothing else comes close), adamantine luster, cubic crystal form (commonly octahedral), and high refractive index that produces the characteristic 'fire' (spectral dispersion) in faceted stones.

Distinguish from cubic zirconia (lower hardness at 8.5, higher dispersion), moissanite (double refraction, different specific gravity), and white sapphire (lower dispersion, no fire). Diamond's hardness is absolute - it can only be scratched by another diamond.