Diamond
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, but diamond is metastable and converts to it at a negligible rate under those conditions. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are used in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.
This article is about the mineral. For the gemstone, see Diamond (gemstone). For other uses, see Diamond (disambiguation).Diamond
Dia[1]
1.CB.10a
1.3.6.1
Hexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Fd3m (No. 227)
12.01 g/mol
Typically yellow, brown, or gray to colorless. Less often blue, green, black, translucent white, pink, violet, orange, purple, and red.
Spinel law common (yielding "macle")
111 (perfect in four directions)
Irregular/Uneven
10 (defining mineral)
Colorless
Transparent to subtransparent to translucent
3.52±0.01
Adamantine
Isotropic
2.418 (at 500 nm)
None
None
0.044
Because the arrangement of atoms in diamond is extremely rigid, few types of impurity can contaminate it (two exceptions are boron and nitrogen). Small numbers of defects or impurities (about one per million of lattice atoms) can color a diamond blue (boron), yellow (nitrogen), brown (defects), green (radiation exposure), purple, pink, orange, or red. Diamond also has a very high refractive index and a relatively high optical dispersion.
Most natural diamonds have ages between 1 billion and 3.5 billion years. Most were formed at depths between 150 and 250 kilometres (93 and 155 mi) in the Earth's mantle, although a few have come from as deep as 800 kilometres (500 mi). Under high pressure and temperature, carbon-containing fluids dissolved various minerals and replaced them with diamonds. Much more recently (hundreds to tens of million years ago), they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites.
Synthetic diamonds can be grown from high-purity carbon under high pressures and temperatures or from hydrocarbon gases by chemical vapor deposition (CVD). Imitation diamonds can also be made out of materials such as cubic zirconia and silicon carbide. Natural, synthetic, and imitation diamonds are most commonly distinguished using optical techniques or thermal conductivity measurements.
Synthetic diamonds of various colors grown by the high-pressure high-temperature technique
Colorless gem cut from diamond grown by chemical vapor deposition
Etymology, earliest use and composition discovery
The name diamond is derived from Ancient Greek: ἀδάμας (adámas), 'proper, unalterable, unbreakable, untamed', from ἀ- (a-), 'not' + Ancient Greek: δαμάω (damáō), 'to overpower, tame'.[159] Diamonds are thought to have been first recognized and mined in India, where significant alluvial deposits of the stone could be found many centuries ago along the rivers Penner, Krishna, and Godavari. Diamonds have been known in India for at least 3,000 years but most likely 6,000 years.[131]
Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage in engraving tools also dates to early human history.[160][161] The popularity of diamonds has risen since the 19th century because of increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns.[116]
In 1772, the French scientist Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an atmosphere of oxygen, and showed that the only product of the combustion was carbon dioxide, proving that diamond is composed of carbon.[162] Later in 1797, the English chemist Smithson Tennant repeated and expanded that experiment.[163] By demonstrating that burning diamond and graphite releases the same amount of gas, he established the chemical equivalence of these substances.[30]