Mohs Hardness Scale

The Mohs Hardness Scale is a qualitative ordinal scale that characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs. The scale is not a linear scale, but somewhat arbitrary in nature. Here’s how the scale is structured, from softest to hardest:

1. Talc (Mohs hardness: 1)
   • Easily scratched by the fingernail.
2. Gypsum (Mohs hardness: 2)
   • Can be scratched by a fingernail.
3. Calcite (Mohs hardness: 3)
   • Can be scratched by a copper coin.
4. Fluorite (Mohs hardness: 4)
   • Can be scratched by a steel knife.
5. Apatite (Mohs hardness: 5)
   • Can be scratched by a steel knife, but with more difficulty than fluorite.
6. Orthoclase Feldspar (Mohs hardness: 6)
   • Can be scratched by a steel file.
7. Quartz (Mohs hardness: 7)
   • Can scratch glass and steel.
8. Topaz (Mohs hardness: 8)
   • Can scratch quartz.
9. Corundum (Mohs hardness: 9)
   • Includes sapphires and rubies, can scratch topaz.
10. Diamond (Mohs hardness: 10)
    • The hardest known natural substance, can scratch all other materials.

The Mohs scale is a simple tool used in identifying minerals and understanding their durability and hardness. However, it’s important to note that the scale doesn’t account for other factors like toughness or brittleness, which can also be important when considering the durability of minerals and gemstones.