gemstone

Diamond

Carbon (C)

Hardness: 10 on Mohs scale (hardest known natural material), Color: Colorless (or colored in fancy varieties like yellow, brown, blue, pink), Luster: Adamantine, Crystal Structure: Isometric (cubic), Cleavage: Perfect octahedral cleavage, Specific Gravity: 3.50-3.53

Identified August 1, 2026More gemstone →

Explore Diamond in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed under high-pressure and high-temperature conditions (approx. 900-1300 degrees Celsius and 45-60 kilobars) in Earth's mantle at depths of 140 to 190 kilometers, brought to the surface via deep-source volcanic eruptions of kimberlite and lamproite magmas, primarily during the Precambrian to Mesozoic eras.

Uses & applications

Widely used as a precious gemstone in fine jewelry and engagement rings, as well as in industrial applications such as cutting, grinding, drilling, and polishing due to its extreme hardness and thermal conductivity.

Geological facts

Diamond is the hardest naturally occurring substance on Earth, yet it is made entirely of carbon, the same element that makes up graphite and charcoal. The high dispersion of light gives cut diamonds their characteristic 'fire' and brilliance.

Field identification & locations

Identified in gemological testing by its extreme hardness, high refractive index (2.417), high thermal conductivity, and adamantine luster. Natural diamond deposits are found globally in ancient cratonic regions, including South Africa, Russia, Botswana, Canada, and Australia.