Kansas Geological Survey, Public Information Circular (PIC) 16
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Kansas Geological Survey, Public Information Circular (PIC) 16
Prev. Page--History
Diamonds are the only mineral of economic value potentially present in kimberlites. Diamonds are the hardest substance known and their brilliance makes them a popular gemstone. They are composed of pure carbon, one of the most common mineral-forming elements, and best known in the form of coal. Diamond is the stable form of carbon at high pressures and temperatures. If the chemistry, the pressure, and the temperature conditions are just right at the depths where kimberlite magma is generated, diamonds can crystallize. Diamonds can be preserved in kimberlite magma, which serves as a kind of high-speed elevator to the surface.
The two types of diamonds commonly recovered from kimberlites are gemstones and industrial diamonds. Industrial diamonds, commonly referred to as bort, are used in industrial tools and equipment, such as drill bits. Because the price of bort diamonds is so low, it is uneconomic to operate a mine that produces only bort. Most economical diamond mines produce somewhere between 20 and 40 percent gem-quality material.
Kimberlite mining causes relatively few environmental problems. Unlike many other ores, kimberlite does not contain potentially harmful sulfides, which can cause water and soil to become acidic. In addition, the process by which diamonds are recovered from the rock is relatively simple. The rock is crushed and the diamonds, being denser, are concentrated, together with some other heavy minerals, using centrifugal diamond pans and vibrating grease tables to which the diamonds stick.
There is no record that diamonds have been found in Kansas, either in kimberlite rock, stream gravels, or glacial deposits. Why some kimberlites contain diamonds and others don't is not well understood. Nonetheless, even without diamonds, kimberlites are scientifically important because they provide clues about the deep subsurface, snapshots of an otherwise inaccessible region deep within the earth.
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Tolman, C., and Landes, K. K., 1939, Igneous rocks of the Mississippi Valley lead-zinc districts, Chapter 3; in, Contributions to a Knowledge of the Lead and Zinc Deposits, E. S. Bastin, ed: Geological Society of America, Special Paper 24, p. 71-103.
Kansas Geological Survey, Public Outreach
Web version July 2000
http://www.kgs.ku.edu/Publications/pic16/pic16_4.html