Diamond usually not polished as a gemstone, as it does not meet the minimum quality criteria for grading. Industrial diamonds are very heavily included, lacking the transparency, brilliance and life that a gem quality diamond must exhibit. Industrial diamonds are somtimes used in their rough diamond form in jewellery. Industrial diamonds are very useful for tools, drills, lasers, abrasives, and other such uses. Only approximately 20% of mined diamonds are of gem quality.
The Diamond Certification Laboratory of Australia (DCLA)
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