Diamond (gemstone) to help authenticate Canadian diamonds. This is a very stringent tracking system of diamonds and helps protect the 'conflict free' label of Canadian diamonds. Currently, gem production totals nearly of cut and polished stones annually, and over of mined diamonds are sold for industrial use each year, as are about of synthesized diamond. Diamond (gemstone) A diamond (from the "adámas", meaning "unbreakable", "proper", or "unalterable") is one of the best-known and most sought-after gemstones. Diamonds have been used as decorative items since ancient times; some of the earliest references can be traced to 25,000 - 30,000 B.C. The hardness of
Volcanic rock of most volcanic rocks tends to increase the silica (SiO) content, mainly by crystal fractionation. The initial composition of most volcanic rocks is basaltic, albeit small differences in initial compositions may result in multiple differentiation series. The most common of these series are tholeiitic, calc-alkaline, and alkaline. Most volcanic rocks share a number of common minerals. Differentiation of volcanic rocks tends to increase the silica (SiO) content mainly by fractional crystallization. Thus, more evolved volcanic rocks tend to be richer in minerals with a higher amount of silica such as phyllo and tectosilicates including the feldspars, quartz polymorphs and muscovite.