Diamond (gemstone) be considered appropriate for use as a gemstone; the other 80% are relegated to industrial use. Of that top 20%, a significant portion contains one or more visible inclusions. Those that do not have a visible inclusion are known as "eye-clean" and are preferred by most buyers, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry. Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. When set in jewelry, it may also be possible to hide certain inclusion behind mounting hardware such as prongs in a way that
Kimberlite significant amounts of forsteritic olivine, with lesser amounts of pyrope garnet, Cr-diopside, magnesian ilmenite, and spinel. Olivine lamproites were previously called group II kimberlite or orangeite in response to the mistaken belief that they only occurred in South Africa. Their occurrence and petrology, however, are identical globally and should not be erroneously referred to as kimberlite. Olivine lamproites are ultrapotassic, peralkaline rocks rich in volatiles (dominantly HO). The distinctive characteristic of olivine lamproites is phlogopite macrocrysts and microphenocrysts, together with groundmass micas that vary in composition from phlogopite to "tetraferriphlogopite" (anomalously Al-poor phlogopite requiring Fe to enter the tetrahedral site).