Wednesday, July 21, 2010
All About Diamonds
Every body know that diamonds is most beautiful stones in over the entire world but a very few people know that what is diamonds and where is it found? Diamond may be up to 3 billion years old, which is much older than their surface host rock. Diamond crystallization originates some 200 kilometers, or 320 miles, beneath the surface and the disaggregated crystals are merely transported to the surface via kimberlite and lamproite pipes. These igneous host rock formations are roughly cylindrical in shape and act as a conduit from the Earth’s mantle to the continental crust. Today, 75-80% of the world’s natural diamonds are used for industrial purposes and 20-25% for gemstones. Diamond may even be found in meteorites.
Diamond is a colourless exceptionally hard mineral (but often tinted yellow, orange, blue, brown, or black by impurities), found in certain igneous rocks esp. the kimberlites of South Africa. It is used as a gemstone, as an abrasive, and on the working edges of cutting tools. Composition: carbon. Formula: C. Crystal structure: cubic. Name derived from the Greek adamas meaning invincible. Relative density 3.50- 3.52. Cleavage eminent along octahedral faces. Fracture conchoidal. Tenacity brittle. Lustre brilliantly adamantine. Refractive index 2.417- 2.419. Dispersion strong 0.044. Diamond crystals form as cubes, octahedra , the most common gem form, and dodecahedra. Colourless to yellow diamonds which have a strong absorbtion line in the violet end of the spectrum are members of the Cape series. Color is usually pale yellow to colorless, but can also be brown, blue, green, orange, red, and black.
The most famous diamond bearing country is South Africa. The first diamond was reported in 1866. By 1869 an 83.5 carat diamond had been found and was named The Star of Africa. It was subsequently cut into a pear shape brilliant weighing 47.74 carats. The Golconda area of Southern India has been the source of some famous diamonds such as the Koh-i-nor (mountain of light 186cts cut to 108.92 cts and now in the Tower of London) and Jehangir. Diamond is widespread in Brazil, most stones being small but of good gem quality. Alluvial diamonds have been found in most states of the USA. White and fancy coloured diamonds such as pinks and pinkish browns are mined at Argyle in North Western Australia. Other important producers are Russia, now the fourth largest producer, and China.
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