The short answer: the Mohs scale ranks scratch resistance from 1 to 10, and for rings the stones that rate around 8 or above, such as diamond, sapphire and ruby, are the best choices for daily wear, while softer gems need more protection. Hardness is only one part of durability, because toughness also matters.
When choosing a ring stone, it helps to know how well it resists scratches and knocks. The Mohs scale is a simple guide.
Hardness chart for ring stones
| Stone | Approximate Mohs hardness |
|---|---|
| Diamond | 10 |
| Sapphire and ruby | 9 |
| Spinel | About 8 |
| Emerald, aquamarine, morganite | About 7.5 to 8 |
| Tourmaline | About 7 to 7.5 |
| Garnet | About 6.5 to 7.5 |
| Tanzanite | About 6.5 to 7 |
| Opal | About 5.5 to 6.5 |
| Pearl | About 2.5 to 4.5 |
These are approximate ranges, and individual stones vary.
Hardness and toughness are different
Hardness is resistance to scratching. Toughness is resistance to chipping or breaking. A hard stone can still chip if it has a direction in which it splits. Emerald, for example, is fairly hard but has inclusions that make it more fragile.
Stability is the third factor
Alongside hardness and toughness, jewellers think about stability, which is how a stone copes with heat, light and chemicals. Some stones can fade in strong sunlight, some dislike sudden changes of temperature, and some are affected by perfume, cleaning products or chlorine. Opal, pearl and kunzite are examples of stones that need gentler handling for these reasons. See kunzite for one example.
What this means for rings
- For daily wear, diamond, sapphire and ruby are the best performers.
- Stones at 7.5 to 8 suit rings with a protective setting.
- Softer stones suit occasional wear, pendants and earrings.
Protective settings
A bezel or halo helps protect softer gems. Lower profile settings reduce knocks.
Everyday dust is harder than some gems
Fine dust contains quartz, which is about 7 on the scale, so stones softer than that can show wear over time. This is why soft stones such as opal and pearl need the most care, and why a polish can bring back the shine on a stone that has been worn for years.
The scale is not even
The Mohs scale is a ranking, not a measurement of equal steps. Diamond at 10 is far harder than sapphire at 9, and the gap between them is much larger than the gap between 8 and 9. That is why diamond keeps its polish so well, and why even a sapphire can show fine scratches over many years.
Storing stones of different hardness
A harder stone scratches a softer one, so a diamond ring kept loose in a box with an opal pendant can mark it. Keep each piece in its own pouch or compartment, and store softer pieces apart. The same idea applies when you wear several rings together: a diamond band beside a softer gemstone ring can wear the softer stone over time. See travel storage for rings.
How to choose
- Decide how often you will wear the ring.
- Match the stone to your lifestyle.
- Choose a setting that protects it.
See cleavage and chips, best settings for sapphire and diamonds. Nothing is made until you approve the design in writing, and our standard making time is 5 to 6 weeks, which can vary with your location and how busy we are. Pieces start from £600.
Frequently asked questions
Is a higher number better? It helps with scratches, but toughness also matters.
Can I wear a soft stone daily? You can with care and a protective setting.
Can you help me choose? Yes, we can talk through your lifestyle.
Do scratches matter? Fine scratches can dull a stone, and a polish can often restore it.
Is a lab grown stone as hard as a natural one? Yes, the same material has the same hardness, and we label each stone clearly.