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Hardness

Corundum Corundum

Hardness: 9
Colour: Can be white or colourless, red, blue, yellow, green, brown, purple, and pink
Streak: White
Lustre: Vitreous to adamantine
Other characteristics: It can have a conchoidal (shell-shaped) fracture

Gemstone quality: The red variety of corundum is known as ruby and all the other colours of corundum are known as sapphire. Both varieties are highly prized gemstones.
Industrial uses: Powdered corundum is an abrasive used to make sandpaper and emery boards.

Emery boards
Corundum is used to make sandpaper and emery boards you use to file your fingernails.

Return to Mohs scale to learn more about hardness.