The Diamond and its characteristics
The name "diamond" describes a nonmetallic mineral that has been for centuries the preeminent gem stone. It occurs in nature in various crystal forms, the most common of which is the octahedron shape or some modification of it.
The diamond possesses several exceptional qualities. It is the only precious stone composed of a single chemical element: crystallized carbon. The strongest acids and alkalis do not affect it, but if heated in air to a high temperature of 900°C it burns to carbon dioxide. Its extreme hardness, which exceeds that of any other known substance, is of great industrial importance; the discolored and very impure diamonds that are unsuitable for gems are used as abrasives.
The optical qualities of the diamond--high light dispersion and refraction--combine with the remarkable transparency and translucence to give the cut gem a great brilliancy and display of prismatic colors. The diamond not only shows a great variety of shape and size but also of color. White, yellow and brown specimens are the most common, with the pure white the most prized of all.
Geologic occurrence
A diamond crystal in the state in which it is recovered from the earth is called a rough diamond, or rough. Rough diamonds occur generally in two types of deposits: (1) in igneous rock masses of kimberlite known as pipes; and (2) in alluvial gravel, both inland and marine, into which they were washed from the kimberlite through some volcanic action or underground pressure.
Recovery from kimberlite rock or sea deposits requires large-scale mining processes while that from alluvial-surface fields may be operated on a small scale and worked by individual diggers.
In order to obtain five tons of diamonds, the approximately yearly output, 125 million tons of ore must be processed; this is about 1 carat* of rough for each 20 tons of rock and gravel.** While only 1 ton of the annual output is appropriate for gems, its value is usually twice the of the remainder, which is only suitable fo industrial use.
Szenberg, Michael. The Economics of the Israeli Diamond Industry. New York: Basic Books, 1973, pp. 11-12
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*1 carat = 0.2 grams
**That's a ratio of 1 to 20,000,000. In copper, zink or lead the ratio varies between 1 to 50 and 1 to 100.
**That's a ratio of 1 to 20,000,000. In copper, zink or lead the ratio varies between 1 to 50 and 1 to 100.
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Moreover, an unrivalled economic tale about artificial scarcity and possibly the only cartel ever that has managed to control not only supply but also demand: The Diamond Invention.
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