As an abrasive (generally synthetically manufactured from bauxite).Colour is caused by a mixture of magnetite, hematite and spinel. Emery: A black massive variety of corundum.Sapphires owe their colour to Fe 2 +, fe 3 + and Ti 4 + inclusions. The name sapphire is the general tem for all other colours of corundum (blue, pink, green, yellow, violet, purple, orange, brown, white, gray, black and colourless). Sapphire: The name sapphire comes from the Latin word for blue, “Sapphires,” which is also thought to have been used in ancient times to refer to lapis lazuli.It owes its colour to both iron and chromium inclusions.
Padparadscha Sapphire: A Rare orange-pink variety of corundum.Ruby owes its colour to corundum impurities. Ruby: Ruby gets its name from the Latin word ”Ruber,” meaning red.They have always been held in very tight regard. Ruby and sapphire, two varieties of corundum are among the oldest known gems to man, dating back many thousands of years. Some corundum even owes its colour to irradiation, or the elements vanadium, cobalt or nickel. Small amounts of metallic elements such as Cr, Fe and Ti can substitute for aluminum in the structure, which gives rise to many colour variations. Pure corundum is rare in nature, and is completely colourless. Furthermore, it can be found in the contact zone between igneous rocks and limestone’s.Ĭorundum has the chemical formula Al 2O 3. Corundum can occur as an accessory mineral in metamorphic rocks, derived from aluminous or carbonate sediments such as crystalline limestone and marbles, mica schist’s and gneisses. It often appears in light-coloured igneous rocks such as desilicated pegmatites, syenites and Nepheline syenites. Generally, these settings are aluminum rich and silica poor. Formation:Ĭorundum forms in a variety of geological settings. The name corundum was first derived either from the Sanskrit word Kuirvinda or from the Indian name for corundum, Kauruntoka. It is unaffected by acids and most environments. For all practical purposes, it is the hardest mineral, second only to diamond. Corundum is a very hard, tough and stable mineral.
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