Carbon is the cosmic product of the “burning” of helium, in which three helium nuclei, atomic number 4, fuse to produce a carbon nucleus, atomic number 12.In the crust of Earth, elemental carbon is a minor component.Before the discovery in 1779 that graphite when burned in air forms carbon dioxide, graphite was confused with both the metal lead and a superficially similar substance, the mineral molybdenite.Pure diamond is the hardest naturally occurring substance known and is a poor conductor of electricity.Q-carbon, which is created by rapidly cooling a sample of elemental carbon whose temperature has been raised to 4,000 K (3,727 °C [6,740 °F]), is harder than diamond, and it can be used to manufacture diamond structures (such as diamond films and microneedles) within its matrix. Each of the “amorphous” forms of carbon has its own specific character, and, hence, each has its own particular applications.All are products of oxidation and other forms of decomposition of organic compounds.Coal and coke, for example, are used extensively as fuels.
Coke and charcoal are nearly pure carbon.) In addition to its uses in making inks and paints, carbon black is added to the rubber used in tires to improve its wearing qualities.
The following products result: (1) diamond proper—distorted cubic crystalline gem-quality stones varying from colourless to red, pink, blue, green, or yellow; (2) bort—minute dark crystals of abrasive but not gem quality; (3) ballas—randomly oriented crystals of abrasive quality; (4) macles—triangular pillow-shaped crystals that are industrially useful; and (5) carbonado—mixed diamond–graphite crystallites containing other impurities.
The successful laboratory conversion of graphite to diamond was made in 1955.
Isolated finds around the world in regions where no sources are indicated have not been uncommon.
Natural deposits are worked by crushing, by gravity and flotation separations, and by removal of diamonds by their adherence to a layer of grease on a suitable table.