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Hardness

Orthoclase Orthoclase

Hardness: 6
Colour: Off-white, yellow, or shades of red, orange and brown
Streak: White
Lustre: Vitreous to dull
Other characteristics: Some crystals may show opalescence and are called moonstone

Gemstone quality: Moonstone is often used in jewellery, but it is not a very valuable gem.
Industrial uses: It is an important constituent in glass. It is also found in granite, a decorative building stone.

Granite
Orthoclase is an important mineral in granite, a decorative building stone.

Return to Mohs scale to learn more about hardness.