Mineral Hardness (Mohs Scale) Reference Calculator

The Mohs Hardness Scale Created in 1812 by Friedrich Mohs, a German mineralogist, this scale ranks minerals from 1 (softest) to 10 (hardest) based on their ability to scratch one another. A mineral can scratch any mineral with a lower number and will be scratched by any mineral with a higher number.

The 10 Reference Minerals 1: Talc (softest, used in talcum powder). 2: Gypsum (fingernail can scratch it). 3: Calcite (a copper coin can scratch it). 4: Fluorite. 5: Apatite (a steel knife can scratch it). 6: Orthoclase feldspar (can scratch glass). 7: Quartz (scratches steel). 8: Topaz. 9: Corundum (sapphire and ruby). 10: Diamond (hardest natural material on Earth).

Common Materials Hardness Fingernail: ~2.5. Copper penny: ~3.5. Steel nail: ~6.5. Glass: ~5.5. Hardened steel file: ~6.5. Sandpaper (silicon carbide): ~9.5. Tungsten carbide: ~9.0. The scale is ordinal, not linear — diamond (10) is roughly 4 times harder than corundum (9) in absolute terms, while the gap between talc (1) and gypsum (2) is much smaller.

Practical Uses Geologists use scratch tests in the field to identify unknown minerals. Jewelers consider hardness when selecting gemstones — stones below 7 on the Mohs scale are considered too soft for everyday ring wear because quartz (7) is present in common dust and will scratch softer stones over time. Industrial applications choose materials based on hardness for cutting tools, abrasives, and wear surfaces.

Beyond Mohs For precise engineering applications, the Vickers, Rockwell, and Brinell hardness tests provide quantitative measurements using calibrated indentation. Mohs scale is qualitative (relative ranking only), while these other tests measure actual resistance to indentation in specific units.