Gemstone hardness chart (Mohs scale)
The Mohs scale ranks a mineral's resistance to scratching from 1 to 10. This chart lists the hardness of the gemstones dealers handle, hardest first.
| Gemstone | Mohs hardness |
|---|---|
| Diamond | 10 |
| Ruby | 9 |
| Sapphire | 9 |
| Chrysoberyl (cat's eye, alexandrite) | 8.5 |
| Spinel | 8 |
| Topaz | 8 |
| Emerald | 7.5 – 8 |
| Aquamarine | 7.5 – 8 |
| Tourmaline | 7 – 7.5 |
| Amethyst and citrine (quartz) | 7 |
| Zircon | 6.5 – 7.5 |
| Garnet | 6.5 – 7.5 |
| Peridot | 6.5 – 7 |
| Tanzanite | 6.5 – 7 |
| Jadeite | 6.5 – 7 |
| Moonstone | 6 – 6.5 |
| Opal | 5.5 – 6.5 |
| Turquoise | 5 – 6 |
| Pearl | 2.5 – 4.5 |
What Mohs hardness means
A harder mineral scratches a softer one. It measures scratch resistance, not toughness: diamond is hardest, but can still chip along cleavage.
Why dealers care
Stones below about 7 can be scratched by household dust, which is mostly quartz. They need more careful settings and storage, and are better in earrings and pendants than rings.
Hardness is not durability
Toughness, cleavage and stability also matter. Opal can crack as it dries, and tanzanite has a cleavage plane, despite their hardness numbers.
Frequently asked questions
Which gemstone is the hardest?
Diamond, at 10 on the Mohs scale. Ruby and sapphire, at 9, come next.
Which gemstones are suitable for everyday rings?
Stones of about 8 and above, such as diamond, sapphire, ruby, spinel and topaz, resist scratching best.