Mineral Hardness Calculator
A 200-Year-Old Scratch Test Still Works
In 1812, mineralogist Friedrich Mohs ranked ten reference minerals by their ability to scratch one another, and that ordinal scale has outlasted virtually every other 19th-century classification tool in geology. It isn't a measurement of absolute hardness in any physical-units sense — it's purely relative, based on which mineral scratches which — but that simplicity is exactly why it still works as a five-minute field identification test with no equipment beyond a few reference picks.
The Reference Scale
A mineral scratches any mineral with a lower or equal Mohs number, and is scratched by any mineral with a higher number.
Because the scale is ordinal, not linear, the actual physical hardness gap between adjacent numbers is not constant — the jump from Corundum (9) to Diamond (10) is far larger in absolute terms than the jump from Talc (1) to Gypsum (2).
Why the Scratch Test Still Holds Up
- Field identification — combined with color, streak, and luster, hardness narrows an unknown mineral down quickly without lab equipment.
- Durability and abrasion resistance — gemstone buyers and jewelers rely on Mohs hardness to judge how well a stone will resist everyday scratching in a ring or bracelet setting.
- Industrial material selection — abrasives, cutting tools, and grinding media are chosen partly based on how their hardness compares to the material being worked.
- Quick comparative picks — common household references (a fingernail is about 2.5, a steel knife blade about 5.5, a piece of quartz about 7) let field geologists estimate hardness even without a full reference kit.
The Mohs Hardness Scale
| Mineral | Mohs Hardness |
|---|---|
| Talc | 1 |
| Graphite | 1.5 |
| Gypsum | 2 |
| Gold / Silver / Galena | 2.5 |
| Calcite / Copper | 3 |
| Fluorite | 4 |
| Apatite | 5 |
| Opal / Turquoise | 5.5 |
| Orthoclase Feldspar / Hematite / Magnetite | 6 |
| Pyrite / Jade | 6.5 |
| Quartz / Amethyst / Garnet | 7 |
| Topaz | 8 |
| Corundum | 9 |
| Diamond | 10 |
Values match this calculator's built-in reference lookup and the standard published Mohs scale.
How to Use This Calculator
- Select a mineral from the list.
- Select Calculate to see its Mohs hardness value and where it falls on the 1–10 scale.
Related Calculations
Pair a hardness reading with the Rock Density Calculator for a fuller field identification profile.