DIMONDS Diamond is the best known gem. It is known as the "king of gems" for its brilliance and for being the hardest mineral on earth. (Foa, p.50) Its characteristics enable it to be used for many different purposes. Since diamonds are the hardest gems on Mohs' scale, they make useful tools for industrial purposes, such as drilling hard materials. However, they are quite rare, which makes them very valuable. Their beauty and brilliance make them perfect for jewelry.
Diamond is made up of carbon. Another form of pure carbon is graphite. Graphite is the stable form of carbon, found at the earth's surface. Despite the fact that they have identical chemical composition, the two minerals are drastically different. Diamond is the hardest known substance and is usually light colored and transparent, while graphite is greasy, easily powdered, and very dark in color. Diamond is the hardest gem on Mohs' hardness scale and graphite is the softest.
diamonds
Diamond lattice
A scattering of "brilliant" cut diamonds shows off...Diamond is very hard because of its dense packing and interlocking atomic arrangement. Graphite, on the other hand, although it is the same element, is more loosely packed and has a six-sided, layered configuration, which makes it soft (Pough, 1991). The differences between graphite and diamonds are accounted for by the conditions in which they are created.
Diamonds form over long periods of time, between 100 km and 200 km below the surface. At this great depth, carbon gets a chance to cool very gradually, forming diamond crystals. When volcanic eruptions occur, magma carries the diamonds up to the surface of the earth. Kimberlite lavas carrying diamonds erupt at anywhere between 10 and 30 km/hour and increase their velocity to several hundred km/hour within the last few kilometers. (Pough, 44) At the surface, this lava cools and turns into Kimberlite rock. That...