Diamond

Diamond is the cubic modification of carbon and, as a naturally occurring solid, is a mineral from the mineral class of elements. Diamond forms mostly octahedral crystals, often with curved and striated faces. Other observed shapes include the tetrahedron, dodecahedron, and cube. The crystals are transparent, colorless or colored by impurities (e.g. nitrogen or boron) or crystal lattice defects green, yellow, brown and more rarely orange, blue, pink, red or gray to black.

Diamond is the hardest natural material. In the Mohs hardness scale, it has a hardness of 10. Its abrasive hardness according to Rosiwal (also absolute hardness) is 140 times greater than that of corundum. However, the hardness of diamond is different in different crystal directions (anisotropy). This makes it possible to grind diamond with diamond. In the diamond powder used for this purpose, the crystals are present in every orientation (statistical isotropy), so that the hardest of them always act on the body to be ground.

Diamond is optically isotropic with high refraction and high dispersion. It shows fluorescence and phosphorescence and is triboelectric. It has the highest thermal conductivity of all known minerals.

The weight of individual diamonds is traditionally expressed in carats, a unit that corresponds exactly to 0.2 grams (see section "Weight in carats"). An untreated, i.e. in particular uncut, diamond is called a rough diamond.

Etymology and history

The name diamond is derived from the Late Latin diamantem, accusative of diamas, a Graecian modification of adamas, acc. adamanta, to Greek ἀδάμας, adámas, "indomitable". In classical Latin, as already in Greek, adamas was the name given to particularly hard materials, such as steel by Hesiod, probably diamond by Plato and Theophrastus, and sapphire by Pliny.

The oldest diamond finds are reported from India, allegedly as early as the 4th millennium BC. Already at that time, diamonds were said to have magical effects, which is why they were also used as talismans. Diamonds were also known to the ancient Romans and were highly valued.

The use of diamonds as tools was already described by Pliny the Elder in his work Naturalis historia, XXXVII 60. Around 600 A.D. the first diamond was reported on the Indonesian island of Borneo, but although India was now no longer the only source, the Indonesian finds remained insignificant because the numbers were too small and the transport to the trading cities too far. It was not until the 13th century that it was discovered that diamonds could be worked, but this was rejected in India as it was said that this would cause the stones to lose their magical powers. Today's typical brilliant cut ­was not developed until around 1910.

In the 18th century, Indian and Indonesian mines gradually became exhausted. When a Portuguese was searching for gold in Brazil, he discovered the first diamond outside Asia. This discovery caused a "diamond rush". The first diamond in the parent rock kimberlite was found in 1869 in Kimberley in South Africa. One year later South Africa took over the role of the main supplier, as finds in Brazil also became rarer.

At the World's Fair in Philadelphia in 1876, a stone circular saw set with diamonds was shown to the general public for the first time. In 1908, diamonds were also discovered on the diamond coast of German Southwest Africa, and in 1955 the first diamond was finally produced artificially. The first diamond on the seabed was not found until 1961. Today, Russia is the main supplier of diamonds.

Other first finds
Year	State
1826	Russia
1851	Australia (first in Australia)
1867	South Africa (first in Africa)
1901	Venezuela
1906	USA (State of Arkansas)
1906	on the territory of what is now the Democratic Republic of the Congo (then the Belgian Congo)
1908	Namibia (then German South-West Africa)
1912	Angola (then Portuguese)
1920	West coast of Africa (Ghana, then British colony Gold Coast)
1969	China
1992	Canada

Play media file Exhibition in Amsterdam, 1955

Classification

In the meanwhile outdated, but still common 8th edition of the mineral systematics according to Strunz the diamond belonged to the mineral class of the "elements" and there to the division of the "semi-metals and non-metals", where it formed an independent group together with chaoite, fullerite, graphite, lonsdaleite and moissanite.

The 9th edition of Strunz's mineral system, valid since 2001 and used by the International Mineralogical Association (IMA), also classifies the diamond in the class of the "elements" and there in the division of the "metalloids and nonmetals". However, this division is further subdivided according to the related chemical elements, so that the mineral is to be found accordingly in the subdivision "carbon-silicon-family", where it forms only together with lonsdaleite the unnamed group 1.CB.10.

Also the systematics of the minerals according to Dana classifies the diamond in the class and department of the same name of the "elements". Here it is together with graphite, lonsdaleite, chaoite and fullerite in the "carbon polymorphs" with the system no. 01.03.06 within the subdivision "elements: Semimetals and nonmetals".