gemstone

Diamond

Carbon (C)

Hardness: 10 on Mohs scale (hardest known natural material), Color: Colorless (or various fancy colors like yellow, brown, blue), Luster: Adamantine, Crystal Structure: Isometric (cubic), Cleavage: Perfect octahedral cleavage in four directions, Specific Gravity: 3.50-3.52

Identified August 1, 2026More gemstone →

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Physical properties

Formation & geological history

Formed under high-temperature and high-pressure conditions in the Earth's mantle, typically at depths of 150 to 250 kilometers (93 to 155 mi), and brought to the surface through deep volcanic eruptions of kimberlite and lamproite magmas.

Uses & applications

Widely used in high-end jewelry, engagement rings, and various industrial applications including cutting, grinding, drilling, and polishing tools due to its extreme hardness.

Geological facts

Diamond is the hardest naturally occurring substance on Earth. It has exceptional thermal conductivity and optical dispersion, giving it its characteristic 'fire' and brilliance when properly cut.

Field identification & locations

Can be identified in cut form by its high refractive index, adamantine luster, and strong fire (dispersion of light into spectral colors). Testing can be done using a thermal diamond tester. Natural diamond is geologically plausible in parts of South America, though cut stones are ubiquitous worldwide.