Diamond

Diamond is the hardest mineral on Earth. It has an exceptional luster and brilliant fire. Hence, these features make it the most highly prized of all gems. A pure, colorless diamond is the most popular. However, other varieties – from yellow and brown to green, pink, blue, grey, red, and black – are also found, depending on the impurities present. A colored diamond is known as fancy.

It is essential to note that the red diamond is the most valuable variety. The opaque, black ‘bort’ (microcrystalline) variety gets its color from graphite inclusions. It is often used industrially. The black type occurs as rounded masses with radiating structures. On the other hand, the dark green diamond derives its color due to exposure to radioactive radium. A diamond may display asterism (a double six-rayed star) due to its inclusions.

It is a known fact that over 3/4th of all mined diamonds are of industrial quality.

Because of the uniform arrangement of their constituent carbon atoms, diamond crystals are well-formed – usually octahedral with rounded edges and slightly convex faces. Their perfect cleavage facilitates the early stages of fashioning, but other diamonds can only polish them. Another shape is the dodecahedral habit that has 12 sides. A diamond may also have a three-sided face, known as a trigon.

A diamond is graded by color, cut, clarity, and carat (weight) – the four c’s.

A rough diamond may be transparent to opaque. It may have a sugar-like surface texture. Also, the cubic habit in a diamond is not very common. Its rough is usually found in a conglomerate of mineral grains and pebbles. Most transparent diamonds are faceted as a brilliant cut, which brings our natural fire. The facets of the stone reflect as much light as possible through the front.

A diamond is the most popular gem to be used in jewelry. It is set in the simplest to the most complicated ones because of its hardness, extraordinary fire, and luster that produces an almost shimmering effect. A diamond may be set in platinum, gold, and silver jewelry. It is used in rings, pendants, brooches, necklaces, earrings, bracelets, crowns, and nose pins.

The volcanic, diamond-bearing kimberlite rock was first identified in Kimberley, South Africa.

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Occurrence

Diamond forms at high temperatures and pressures 80km (50 miles) or more underground. When India and later Brazil were the leading producers, most diamonds came from secondary sources, such as river gravels. However, since the discovery of diamond in kimberlite rock in South Africa (around 1870), its extraction has involved processing vast quantities of stones.

Australia is the primary producer today; other localities include Botswana, Congo, Sierra Leone, Ghana, Namibia, the USA, Brazil, and the former USSR.

Diamond Properties

Specific Gravity: 3.52
Refractive Index: 2.42
Birefringence (DR): None
Luster: Adamantine
Crystal Structure: Cubic
Composition: Carbon
Hardness: 10

Diamond Imitations

A diamond may be imitated by any colorless stone, glass, or artificial gems like YAG (yttrium aluminum garnet). None of these is an exact copy, though.