- 1/07/11 - Gemstone Information – Moh’s Hardness Scale
Education
The Mohs scale of mineral hardness is based on the ability of one natural sample of matter to scratch another. The samples of matter used by Mohs are all minerals. Minerals are pure substances found in nature. Rocks are made up of one or more minerals.
Following is the Gemstone Characteristic of each individual stone.
| Gemstone Name | Specific Gravity | Moh’s Hardness | Refractive Index |
| Alexandrite | 3.68 – 3.78 | 8.5 | 1.746 – 1.755 |
| Amethyst | 2.65 | 7.0 | 1.532 – 1.554 |
| Aquamarine | 2.63 – 2.91 | 7.5 – 8.0 | 1.567 – 1.590 |
| Cat’s Eye | 3.68 – 3.78 | 8.5 | 1.746 – 1.755 |
| Chalcedony | 2.65 | 7.0 | 1.544 – 1.553 |
| Chrysoberly | 3.68 – 3.78 | 8.5 | 1.746 – 1.755 |
| Chrysoprase | 2.65 | 7.0 | 1.530 – 1.550 |
| Citrine | 2.65 | 7.0 | 1.532 – 1.554 |
| Color Change Garnet | 3.50 – 4.30 | 6.5 – 7.5 | 1.880 – 1.900 |
| Diamond | 3.51 | 10 | 2.417 |
| Garnet | 3.50 – 4.30 | 6.5 – 7.5 | 1.730 – 1.760 |
| Indicolite | 3.03 – 3.25 | 7.0 – 7.5 | 1.610 – 1.640 |
| Moonstone | 2.55 – 2.76 | 6.0 – 6.5 | 1.518 – 1.526 |
| Onyx | 2.65 | 7.0 | 1.531 – 1.539 |
| Opal | 1.98 – 2.25 | 5.5 – 6.5 | 1.440 – 1.460 |
| Peridot | 3.22 – 3.45 | 7.0 | 1.635 – 1.690 |
| Quartz | 2.65 | 7.0 | 1.544 – 1.553 |
| Rhodolite | 3.50 – 4.30 | 6.5 – 7.5 | 1.740 – 1.770 |
| Rose Quartz | 2.65 | 7.0 | 1.540 – 1.550 |
| Rubellite | 3.03 – 3.25 | 7.0 – 7.5 | 1.610 – 1.640 |
| Ruby | 3.96 – 4.05 | 9.0 | 1.757 – 1.779 |
| Spessartite | 3.50 – 4.30 | 6.5 – 7.5 | 1.790 – 1.810 |
| Spinel | 3.58 – 4.06 | 8.0 | 1.712 – 1.717 |
| Sunstone | 2.55 – 2.76 | 6.0 – 6.5 | 1.560 – 1.572 |
| Topaz | 3.50 – 3.60 | 8.0 | 1.607 – 1.627 |
| Tourmaline | 3.03 – 3.25 | 7.0 – 7.5 | 1.603 – 1.655 |
| Tsavorite | 3.50 – 4.30 | 6.5 – 7.5 | 1.739 – 1.744 |
| Zircon | 4.60 – 4.70 | 7.5 | 1.777 – 1.987 |
* Please do use only as reference
The Mohs Scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material.
The Specific Gravity is the ratio of the density (mass of a mineral volume) of a substance to the density (mass of the water) of a reference substance.
The Refractive Index of a substance is a measure of the speed of light in that mineral.