What is Corrundum?
Corundum is the mineral name of a family of gems which includes sapphire and ruby. Corundum is 9 on the Mohs' scale, and is the natural material which is second only to diamond in hardness.
Corundum is a simple mineral, essential composed of aluminium and oxygen. Ruby and sapphire are therefore very closely related, and although have similar physical properties, it is the colour that distinguishes them.
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