Mohs scale of mineral hardness Reference Libraries
Corundum is the crystalline form of aluminium oxide and one of the rock-forming minerals. Corundum is naturally clear, but can have different colors when impurities are added. Transparent specimens are used as gems, called ruby if red, while all other colors are called sapphire. The word corundum comes from the Hindi kurand. The oxygen atoms in corundum are arranged in a hexagonal...
- A coin originally worth six pennies Scots, and later three; held equivalent to an English halfpenny.
- (in plural) Money; cash.