North America Diamonds

UNITED STATES: Although numerous kimberlites and lamproites are scattered from New York to Wyoming and Michigan to Arkansas, diamond discoveries and mining have been minimal in the United States, restricted to Arkansas and, now, Colorado.
Near Murfreesboro, Arkansas, from what is now known to be a lamproite pipe, more than 100,000 stones averaging 0.25 carat each were produced between 1907 and 1933. Now Crater of Diamonds State Park, the locality is a stop for hobbyists and tourists. The "State Line Kimberlite District" along the Colorado-Wyoming border is home to the only operating diamond mine in the U.S., started at Kelsey Lake, Colorado, in June 1996. The largest diamond found so far is 28.3 carats, and about 25% of the 20,000-carat annual production is of gem quality.

CANADA: With much of Canada underlain by ancient bedrock, the existence of diamond-bearing kimberlite has been considered very likely, particularly with tantalizing diamonds found in Wisconsin in deposits swept down by glaciers from up north. Now the country is home to the latest major diamond discovery.

Intermittent exploration for kimberlites by major companies was unsuccessful through the 1980s. But Chuck Fipke, head of Dia Met Minerals, persevered and in April 1990 located a kimberlite under Point Lake. Eventually, his company, with partner BHP Minerals, found more than 100 kimberlites on their claims; 42 contain diamonds. Five small pipes, to be operated as if they were one mine, are scheduled to start production in the second half of 1998.