The Mineral Hardness Scale – The Mohs Scale

Mineral hardness - Mohs Scale

Every crystal have various degree of hardness which has been measured by The Mohs Scale. Devised by Friedrich Mohs, an Austrian professor of mineralogy, it has been used to measure hardness for over two centuries. The Mohs scale classifies crystals from the softest (1) to the hardest (10). Below are some examples:

Hardness 1

  • Very soft, can be scratched or fall apart with fingernail. – Talc

Hardness 2

  • Easily scratched with fingernail. – Gypsum

Hardness 3

  • Can be scratched with a coin (copper penny). – Calcite

Hardness 4

  • Can be carved/scratched with a knife. – Fluorite

Hardness 5

  • Can be carved with a knife with difficulty; can be scratched by glass.- Apatite

Hardness 6

  • Can be carved/scratched with glass. Cannot be scratched by a knife. – Orthoclase

Hardness 7

  • Can scratch glass easily. – Quartz

Hardness 8

  • Can scratch glass very easily. – Topaz

Hardness 9

  • Can scratch/cut Topaz and glass, and can be scratched by a diamond. – Corundum (Sapphire and Ruby)

Hardness 10

  • No other minerals will scratch it, but can scratch all other minerals. – Diamond


Image Credit: Hazel Gibson –

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