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The Mohs scale of mineral hardness was developed by German mineralogist, Frederich Mohs in 1812. The scale is used to characterize stones relative hardness and scratch resistance. The method of determining hardness is by testing the ability of a harder stone to scratch a softer stone. The scale ranges from 1 to 10 with 1 being the softest and 10 being the hardest. One thing to keep in mind is that the scale is purely an ordinal scale. That being said, sapphires are twice as hard as topaz and diamonds are four times as hard as sapphires, despite their numbers on the Mohs hardness scale.
A mineral's hardness is its ability to resist scratches. A mineral's toughness is its ability to resist being fractured.
Below is a list of some of the most common gemstones we work with, including their ranking on the Mohs hardness scale as well as its toughness.
| Gemstone |
Mohs Hardness Scale |
Toughness* |
| Diamond |
10 |
Good |
| Sapphire |
9 |
Usually excellent |
| Ruby |
9 |
Usually excellent |
| Alex andrite |
8.5 |
Excellent |
| Spinel |
8 |
Good |
| Aquamarine |
7.5 |
Good |
| Emerald |
7.5 |
Poor to good |
| Amethyst |
7 |
Good |
| Citrine |
7 |
Good |
| Malaya Garnet |
7 |
Fair to good |
| Rose Quartz |
7 |
Good |
| Smoky Quartz |
7 |
Good |
| Tourmaline |
7 |
Fair |
| Peridot |
6.5 |
Fair to good |
| Moonstone |
6 |
Poor |
| Tanzanite |
6 |
Fair to poor |
| Opal |
5 |
Very poor to fair |
| Turquoise |
5 |
Generally fair |
| Pearl |
2.5 |
Usually good |
*Toughness scale: poor, fair, good, excellent
If you are looking for a durable stone, diamonds, sapphires and rubies are the best options.
