Much better known to the general public as ruby and sapphire, the mineral species corundum is a commonly distributed oxide of aluminum that ranks virtually stone in hardness and quite often occurs so abundantly that it’s mined for coarse purposes. Nevertheless, clear gemstone varieties are less typical than the program coarse types, among which “emery” is common to craftsmen as the coating on abrasive wheels and also emery paper. In North America, much coarse corundum continues to be mined from deposits in Canada as well as the Eastern with the US, while specific gem quality material continues to be acquired in huge amount from this site.
Several specimens exhibit the lovely effect recognized as “asterism”, developing the ever popular star sapphire plus star ruby.
By custom, the person species name ruby is used and then gem material of clean rigorous red, any other colors being sapphire. So it’s precise to target green, blue, yellow, purple as well as colorless corundum as being sapphire.
Another variety less translucent compared to gem grades, is viewed as “adamantine spar”, and it is noted chiefly for the bronzy brown chatoyancy of its. Emery is just incredibly impure considerable corundum where a significant quantity of black magnetic oxide from iron is provided, namely “magnetite”.
The title corundum is a modified form of the “Sanskrit “word of unknown initial significance except for the application of its for this mineral species, while sapphire is produced from the old Greek word for blue. It seems the second phrase might have been used initially to the next blue gemstone, likely lapis lazuli, and was later placed on the azure variety of corundum.