Vol. 29, No. 5 #3 (October 2006). Are Diamond Mines in Wyoming's Future?.

• Author: By Wayne M. Sutherland

Wyoming Bar Journal

2006.

Vol. 29, No. 5 #3 (October 2006).

Are Diamond Mines in Wyoming's Future?

WYOMING LAWYEROctober 2006/Vol. 29, No. 5Are Diamond Mines in Wyoming's Future?By Wayne M. Sutherland

Diamonds, composed of pure carbon, are the hardest naturally occurring mineral found on the surface of the earth. They form under extreme pressure and high temperature at great depths within the earth's mantle. Diamonds arrive at the surface through volcanic processes that carry them upward in rare magmas (melted rocks) known as kimberlites or lamproites. A few other rock types may transport diamonds from the mantle, but they have not yet hosted commercial diamond production. Both kimberlites and lamproites are found in Wyoming, as are some less well-known diamondiferous and potentially diamondiferous rocks. The major value of diamonds is for gemstones. A diamond mine is based on the presence of gem-quality diamonds (larger is always better). The smallest size of recoverable diamonds, when defining ore reserves, is tailored to each individual mine and mill. A mine's reserves represent the economic material around which a mine is designed. Some of Canada's large mines currently designate diamonds in the 2 to 3 millimeter size range as the smallest used in their ore reserve calculations. Smaller stones, when recovered, are also used but do not figure in these calculations. Low-quality or extremely small diamonds are used as abrasives, but are not profitable to mine in the absence of gems.

Similar to other valuable minerals such as gold, diamond mining begins with extensive exploration followed by claim-staking where the minerals are federally-owned, or by leasing of state- or privately-owned minerals. However, finding diamond deposits is much more difficult than locating other minerals. Even in a world-class diamond mine, diamonds account for less than one part per million in the host rock!

Diamond exploration may include a sampling program to locate occurrences of tiny mineral grains, such as pyrope garnets and chromian diopside (known as indicator minerals). Concentrations of indicator minerals point to the potential presence of nearby hidden diamond deposits. Further exploration may involve geophysical surveys and drilling to identify and determine the size of kimberlites or other diamond host rocks. Once a host rock has been...