Diamond

Diamond is a crystalline form of pure carbon and the hardest known natural material, rating a perfect 10 on the Mohs scale. Each carbon atom is bonded to four others in a rigid three-dimensional tetrahedral lattice, giving the mineral its extreme hardness and high refractive index.

Diamonds are most famous as gemstones, valued for their brilliance, fire (dispersion of light into spectral colors), and durability. They range from colorless to yellow and brown, with rare and valuable "fancy" colors including blue, pink, green, and red.

Beyond jewelry, diamond's hardness and thermal properties make it vital industrially. Both natural and lab-grown diamonds are now widely available, chemically identical but distinguishable by their origin.

Natural diamonds form deep in the Earth's mantle, roughly 150 kilometers or more below the surface, where intense pressure and temperatures around 900-1300 degrees Celsius crystallize carbon into the diamond lattice. Most are extremely old, billions of years in age.

They are carried rapidly to the surface by deep-sourced volcanic eruptions that produce kimberlite and lamproite pipes, the primary rock hosts from which diamonds are mined. Erosion of these pipes also concentrates diamonds in alluvial (river and beach) placer deposits.

Major producers include Russia, Botswana, Canada, the Democratic Republic of Congo, Australia, and South Africa. Diamonds can also be synthesized in laboratories by high-pressure high-temperature (HPHT) or chemical vapor deposition (CVD) methods.

Look for an exceptionally hard, brilliant, transparent stone with unmatched luster (adamantine), strong fire, and a hardness of 10, meaning it scratches all other gem materials and cannot be scratched by them.

Diamond is singly refractive, has high thermal conductivity (the basis of electronic diamond testers), and shows sharp, crisp facet edges. Rough crystals often form octahedra.

Look-alikes include cubic zirconia (softer at 8-8.5, denser, doubly... no, singly refractive but lower dispersion pattern), moissanite (hardness 9.25 but doubly refractive, showing facet doubling and more fire), white sapphire (softer, less brilliant), and glass (much softer). A thermal/electrical tester and observing double refraction help separate moissanite; gemological testing confirms natural versus lab-grown.

Diamond's most famous use is in fine jewelry, especially engagement rings, where the round brilliant cut maximizes brilliance and fire. Value is assessed by the "Four Cs": carat weight, cut, color, and clarity, with rare fancy colors commanding premium prices.

Industrially, diamond's extreme hardness makes it essential for cutting, grinding, drilling, and polishing tools, and its thermal conductivity and optical properties are used in electronics, optics, and scientific instruments. Most industrial diamond is now synthetic.

Lab-grown diamonds are chemically identical to natural ones and increasingly used in both jewelry and industry. In folklore diamond symbolizes strength, purity, and eternal love; it is the April birthstone.