Created by German mineralogist Friedrich Mohs in 1812, the Mohs scale of hardness is one of the most practical tools in a jeweller’s kit. It ranks minerals from 1 (softest) to 10 (hardest) based on their ability to scratch one another — and for anyone choosing a gemstone for an engagement ring or a piece of jewellery they plan to wear every day, it is essential knowledge.
The fundamental principle is simple: each mineral on the scale can scratch those ranked below it, while being susceptible to scratching by those ranked above. Diamond, at 10, can scratch everything. Talc, at 1, can be scratched by almost anything — including your fingernail.
But the scale is not linear. The hardness gap between corundum (9) and diamond (10) is far greater than the gap between talc (1) and gypsum (2). And minerals sharing the same ranking can still scratch one another.
The Mohs Scale: Minerals and Their Everyday Equivalents
| Position | Mineral | Common Equivalent | Jewellery Examples |
|---|---|---|---|
| 1 | Talc | Fingernail | — |
| 2 | Gypsum | — | Amber |
| 3 | Calcite | Copper coin | Ivory, coral, pearl |
| 4 | Fluorite | — | — |
| 5 | Apatite | Glass | Obsidian |
| 6 | Feldspar | Steel file | Labradorite, moonstone |
| 7 | Quartz | — | Amethyst, citrine, rose quartz |
| 8 | Topaz | — | Topaz, spinel |
| 9 | Corundum | — | Sapphire (all colours), ruby |
| 10 | Diamond | — | Diamond |
What This Means for Your Jewellery
Hardness is one of the most important factors when choosing a gemstone for a ring — particularly an engagement ring worn every day. As a general guide:
- 7 and below: Suitable for occasional wear or earrings and pendants, but vulnerable to scratching from everyday dust and grit (which contains quartz particles at hardness 7). Requires careful storage and handling.
- 7.5–8: Good durability for regular wear with some care. Spinel and topaz sit here.
- 9–10: Excellent for daily wear in ring form. Sapphires and diamonds are the benchmark for engagement rings precisely because of this.
The Gemstones We Work With Most
At Nude Jewellery, we work primarily with stones at the harder end of the scale — chosen not just for their beauty, but for their ability to last a lifetime of daily wear.
Sapphire — Mohs 9
Sapphire is corundum, and at hardness 9 it is one of the most durable gemstones available. All sapphires — regardless of colour — share this hardness rating, making them an exceptional choice for engagement rings.
- Teal sapphires — a blue-green stone with a unique colour-shift, increasingly popular for non-traditional engagement rings
- Pink sapphires — soft and romantic, with the same hardness as their blue counterparts
- Violet sapphires — a deeper, more unusual alternative to the classic blue
- Blue sapphires — the traditional choice, timeless and exceptionally durable
Tsavorite Garnet — Mohs 7–7.5
Tsavorite is a vivid green garnet with exceptional brilliance — often compared to emerald but with greater clarity and durability. At 7–7.5 on the Mohs scale, it sits at the lower end of what we consider suitable for daily ring wear, and we typically recommend a protective setting. Explore our garnet and tsavorite collection.
Amethyst vs Violet Sapphire — A Tale of Two Purple Stones
This is one of the most common comparisons we are asked about, and the Mohs scale tells a significant part of the story.
Amethyst is a variety of quartz, sitting at hardness 7. It is a beautiful stone — rich purple, excellent clarity, and very accessible in price. However, at hardness 7, it sits right at the threshold of vulnerability. Everyday dust contains quartz particles, which means an amethyst ring worn daily can gradually develop surface scratches over time. For rings, we recommend amethyst in protective settings, or for occasions rather than every day. For earrings and pendants, it is an excellent choice. Browse our amethyst jewellery collection.
Violet sapphire, by contrast, sits at hardness 9 — the same as all corundum. It offers a similar purple hue to amethyst but with dramatically superior durability, making it a far better choice for an engagement ring or a piece intended for daily wear. If you love the colour of amethyst but want a stone that will last a lifetime on your finger, a violet sapphire is worth serious consideration.
A Note on Setting and Stone Security
Hardness measures resistance to scratching, but it is not the same as toughness — a stone’s resistance to chipping or breaking. Some hard stones can be brittle. This is why the setting matters as much as the stone itself. A well-designed claw or bezel setting protects the girdle of the stone and reduces the risk of chipping from impact. Our designers always consider both hardness and toughness when recommending stones and settings for pieces intended for daily wear.
If you are unsure which stone is right for your lifestyle, book a consultation at our London studio — we can walk you through the options in person.
EXPLORE OUR GEMSTONE COLLECTIONS