The sample is about 13x13 cm and is from Ticonderoga, New York. This sample of carbon in graphite form is displayed in the Smithsonian Museum of Natural History. The Cullinan diamond, found in South Africa in 1905, weighted 3,106 carats. Before that period, only elements such as copper, silver, gold, mercury, lead and of course carbon were known, which already had accompanied the history of. Carob seeds were once used as measures of weight. Boron carbide, B 4C, is the hardest next to diamond but several of the metal carbides are extremelyhard and find application as cutting edges on high speed tools.ĭiamonds and other precious gems are sometimes measured in carats, a term derived from the Greek word for a carob seed. While diamond is the hardest substance, several carbon compounds called carbides rival its hardness. They are used for diamond drills and abrasives. They are slightly less dense than diamond and are somewhat tougher and harder. Imperfectly formed crystalline forms of diamond are called bort and black diamond. Carbon binds to oxygen to form the carbonate ion CO 3 2- and contributes to an important class of minerals, the carbonates.Ĭarbon has a density of 2.26 in the graphite form and 3.51 in the diamond form. The field of organic chemistry is primarily the chemistry of the compounds of carbon. Many of the chemicals in living organisms are hydrocarbons. Carbon forms more chemical compounds than any other element except hydrogen.
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