Kyanite, rutile, graphite, diamond (eclogitic xenoliths). (schists) pyrope-rich garnet, spinel, phlogopite, omphacitic clinopyroxene, (metamorphosed limestones) kyanite, sillimanite, dumortierite, chlorite (syenites) spinel, rutile, chondrodite, “ hornblende”, phlogopite, calcite This procedure is known asĪndesine, oligoclase, nepheline, scapolite Produced as a special product with slow deposition and controlled growth on aĬoil in an oxyhydrogen flame, as for jewelry use. In regional or contact, high-grade metamorphic aluminous rocks,Īnd some advanced argillic and potassic hydrothermal alteration assemblages ĭue to its high melting point (2,040 ° C or 3,700 ° F). Pegmatites primary or a reaction product in eclogitic xenoliths in Geological environments in syenite and monzonite, and some quartz-free (Boehmite), observed on large blocks (Georgia, USA).ģ.98 – 4.1 g/cm3 (Measured) 3.997 g/cm3 (Calculated) Hexagonal crystals sometimes tapering to a pyramid, parting, luster, Chromium produces red (ruby) and combinations of iron and titanium produce blue (sapphire). Colorless when pure, but trace amounts of various metals produce almost any color. Name: Probably from the Sanskrit kurivinda, for ruby, through the Tamil kurundam It forms in syenites certain pegmatites and in high-grade metamorphic rocks. Corundum can also be massive or granular. Corundum crystals are generally hexagonal, either tabular, tapering barrel-shaped, or dipyramidal. Ruby forms a continuous color succession with pink sapphire only stones of the darker hues are considered to be ruby. An aluminum oxide, corundum is commonly white, gray, or brown, but gem colors include red ruby and blue, green, yellow, orange, violet, and pink sapphire. Ruby and sapphire are gem varieties of corundum. The name corundum comes from the Sanskrit kuruvinda, meaning “ruby” the name given to red corundum. Corundum from Jagdalik, Kabul Prov., AfghanistanĬorundum is the hardest mineral After diamond on Earth.

Corundum from Sackett mine, Chester, Hampden Co., Massachusetts, United States.

Corundum blue