Once believed to be present only in kimberlite, in 1979 commercial-grade diamonds were found in a deposit of olivine lamproite in Western Australia. Six years later, production began at the Argyle diamond pipe, and the mine has since become the single greatest producer of carats per year. The vast majority of the diamonds extracted from the mine are utilized for industrial purposes, but approximately 5 percent are suitable for use as good quality gemstones. The discovery and profitability of the Argyle diamond pipe has prompted the examination of many other lamproite beds, including several found in the United States.