Diamonds are rare beautiful and mysterious gemstones, with superlative physical qualities. They can only be scratched by other diamonds, this makes them retain their luster and hold polish well. Diamonds have been used as treasured gemstones throughout all generations. In ancient India, diamonds were used as a religious symbol, while early human history indicates that diamond was used in tools engravings. An increase in demand in the 19th century raised the popularity of diamonds. The growth of the world economy improved polishing skills, and innovative campaigns are some of the factors that have also contributed to the popularity of diamonds. Diamonds are judged on color, carat, cut, and clarity.
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For diamonds to reach the earth’s surface they take a journey that lasts 3 billion years, Experiments on the diamond and its high density give a clear indication that diamonds crystallize at very high pressure. Diamonds are created through geological processes, deep within the earth at a depth of more than 250 miles in the earth’s mantle. After the formation, other geological processes help to bring diamonds to the surface.
Formation of Diamonds
For a diamond to be formed, high pressure, usually between 50 and 60 kilobars is required. The accompanying temperature should be relatively low, usually between 900 and 1300 degrees centigrade. That is why diamond is only formed at the earth’s mantle because this is the only place where such conditions can are found.
The melting of rocks in the mantle, or the upper surface of the earth, provides carbon that makes up the diamonds. Changing temperatures in the upper section of the mantle usually forces carbon atoms to move deeper in the crust where it melts to form a new rock with a reduction in temperature. If there is the pressure and temperature are right during the process of melting, and the bonding of the right atoms, a diamond is formed.
In case the pressure fall or temperature rises or both, the diamond crystal formed may melt or get dissolved into the inner section of the mantle. If the diamond is formed, it may take millions of years to get to the surface.
The carbon found in the diamonds can be from both organic and inorganic sources. Eclogitic diamonds are formed from organic matters that are pushed deep down to the earth’s mantle from the earth’s surface through a process known as subduction. Harzburgitic diamonds are made up of inorganic carbon originating from the Earth’s mantle. A closer study of the two diamonds shows that they have different carbon ratios.
The crystal structure of diamond has a cubic atom arrangement resulting in many different facets that can be a cube, tetrakis hexahedron, or rhombicosidodecahedron. The diamond crystal can have extended edges or rounded-off edges. Diamond crystals can be found intertwined or separate. These characteristics and shapes of diamonds are a result of external conditions during the formation.
In other instances, very tiny diamonds known as nanodiamonds or micro diamonds are a result of high impacts in meteorite craters. During such events, high pressure combined with relatively low temperature leads to diamond formations.