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The hardness of the diamond

Published : 2017-03-05 14:29:42
Categories : Diamond

Who could believe, admiring the sumptuous brilliancy and hardness of the diamond, that this stone has the same chemical composition as this piece of coal, all black and dirty?

Indeed, the diamond, as the piece of coal is composed only of carbon. The big difference is that in the case of diamond, carbon atoms are organized in a very different molecular network from that of coal.

This crystallographic organization gives it its  physical properties characteristics, namely, among other things, its exceptional hardness and its brilliance. In the natural state, formed by the enormous pressures and temperatures of the center of the earth, the crystalline lattice of the coal (arranged in atomic layers which can slide on each other) has been modified, each carbon atom has bound to its neighbors to give a rigid crystalline lattice and, to the rough diamond crystal a regular shape, the most generally octahedral.

Rough diamond

It is possible, by applying in the laboratory to a piece of coal enormous temperatures and pressures, to make diamonds. But, alas, they are of shapes and qualities unsuitable for jewelery and can only be used in the industry. It is for their exceptional hardness (index 10 on the Mohs scale) that diamonds are used in the industry. Indeed, only another diamond can scratch it and, for polishing, jeweler artisans  use surfaces covered with diamond powder.

Contrary to the popular belief, it is not because the diamond has an exceptional hardness that it is unalterable. If it is resistant to acids, it is unfortunately not necessarily to shocks ! This feature is used by the jeweler artisans to cleave the diamond according to a cleavage plane determined beforehand after a meticulous examination of the rough stone.

Clivage du diamant

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