There are many types of gemstones in the world, all of different gem families, colors, and hardnesses. Gem hardness is rated on the Mohs scale of hardness, which assigns numbers from 1 to 10, with 10 representing the hardest. The intervals between the values are not equal. The numbers for a gemstone can vary depending on the exact make up of a particular stone. The test uses scratching for the basis of hardness. A harder mineral will scratch a softer one, but not the other way around. Hardness is not an indication of toughness or strength. Hard minerals can be brittle. Knowing the hardness of your gemstones can help you care for them.
A gemstone with a hardness of:
- 1-2 can be scratched by a fingernail
- 3 can be scratched by a copper coin
- 4-5 can be scratched by a knife
- 6-8 can scratch glass
- 9-10 can cut glass
