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Friday, January 21, 2011

Diamond the Hardest of all Gems

Photo by Subarcticmike
The very name for the diamond is “adamant” meaning roughly that it is indestructible.  The gem we call diamond was known to the ancients when practically the entire earth’s supply came from the region around Golconda, India.  This region in India supplied most of the diamonds in the world until the discovery of alluvial diamonds in Brazil in 1729.  The diamond fields of Brazil produced most of the world’s diamonds for almost a century until diamonds were discovered in South Africa in 1867.  This led to the discovery of diamonds in an ultramafic rock that was named kimberlite after the South African town of Kimberly where the new rock was discovered.

A diamond crystal in a matrix of kimberlite. USGS

The other source of diamonds during antiquity was from western Borneo where they are found in alluvial deposits of Eocene age.  Most of the stones found in these deposits are small and of poor quality.  These diamonds are still being mined mainly by artesianal methods under primitive methods.  To this day nobody has ever discovered the primary source of these diamonds.

During the post World War II period extensive deposits of diamonds were discovered in the Soviet Union by tracing a special type of pyrope garnet that is in high in chromium to its source.  The source was found in kimberlite pipes in Siberia.  Several mines were opened causing the Soviet Union to become one of the world’s largest producers of diamonds.

A princess cut diamond mounted in a ring.
Photo by Stephen Durham

After the discoveries in the Soviet Union the scene shifted to Australia where a new type of deposit was discovered in a type of rock called lamproite.  This has resulted in the development of the largest diamond mine on earth, the Argylle Mine.  Some pf the diamonds found in this mine are colored purple an extremely rare type of diamond.

The diamond discoveries in the Soviet Union and Australia led to the discovery of kimberlite deposits in Canada, Brazil and India.  There are also deposits producing diamonds in Arkansas and eastern Colorado and Wyoming

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