In short: the Mohs scale is a ten-step scale of relative hardness that ranks minerals by which one scratches which — from talc (1) to diamond (10). It tells you about scratch resistance, but not about resistance to knocks and breakage. For a ring you wear every day, choose stones rated about 7 and above, such as agate, onyx or cubic zirconia. Soft stones like amber, pearls, coral and malachite are better suited to earrings and pendants.
Why does one stone still look new after years, while another loses its polish within a few months? Most often it comes down to hardness. Gemstones and ornamental stones vary enormously, and the simplest tool for comparing them is the Mohs hardness scale. We explain how to read it, why the number isn’t everything and how to wear jewelry with different stones so it stays beautiful for a long time.
The scale of mineral hardness was devised in 1812 by the German mineralogist Friedrich Mohs. Instead of using instruments, he compared the hardness of minerals in a simple way: by checking which one scratches which. A mineral that leaves a scratch on another is harder than it. On that basis he chose 10 reference minerals and arranged them from softest to hardest, on a scale from 1 to 10.
In mineralogy, hardness means resistance to scratching or abrasion of the surface. Any other mineral can be placed between the steps: if it scratches apatite (5) but is itself scratched by orthoclase (6), its Mohs hardness is about 5.5. That’s why hardness is often given as a range, such as 6.5–7.
| Level | Reference mineral | For comparison |
|---|---|---|
| 1 | talc | greasy to the touch, easily scratched by a fingernail |
| 2 | gypsum | a fingernail leaves a scratch on it |
| 3 | calcite | scratched by a copper coin, but not by a fingernail |
| 4 | fluorite | a steel knife scratches it easily |
| 5 | apatite | a knife scratches it with noticeable resistance |
| 6 | orthoclase | scratches glass; a knife no longer scratches it |
| 7 | quartz | scratches steel |
| 8 | topaz | scratches all minerals lower on the scale |
| 9 | corundum (e.g., ruby or sapphire) | scratches topaz |
| 10 | diamond | scratches all the others |
Mineral hardness
Mohs Scale — Cheat Sheet
This 10-step scale is ordinal: it tells you which mineral is harder, but not by how much. The gaps between the steps are very uneven. Diamond (10) is many times harder than corundum (9), and the difference between them is far greater than between talc and gypsum.
Precise hardness measurements are made in laboratories. The best-known method is the Vickers test: a pyramid-shaped indenter is pressed into the material and the size of the impression is measured. When choosing jewelry, the Mohs hardness scale is all you need — it’s the order that counts, not the exact figures.
A curiosity: kyanite has a hardness of about 4.5–5 or 6.5–7, depending on the direction within the crystal. In most jewelry stones such differences are small, which is why charts give a single number or a narrow range.
The most common mistake when choosing a stone is treating this number as a measure of overall durability. The scale answers the question “Will the stone scratch?” but not “Will it crack if I hit my hand on a door frame?” Minerals of the same hardness can behave quite differently, because other properties determine resistance to impact:
Inclusions and the cut matter too. The sharp edges of a faceted cut chip more easily than a smooth, domed cabochon. So look not only at a stone’s place on the scale, but also at the type of stone, the cut and the setting.
Jewelry rubs against all kinds of materials every day. A fingernail rates about 2.5, 925 sterling silver about 2.5–3, and a steel knife and window glass about 5.5. The biggest threat, though, is ordinary dust and sand — they contain quartz particles (7). That’s why minerals with a hardness below 7 gradually turn dull from countless tiny abrasions, for example when you dry your hands.
In practice, three thresholds are useful:
The values are approximate — mineralogical sources give them as ranges, because they depend on the variety and structure of the specimen.
| Stone | Hardness (Mohs) | How to wear it |
|---|---|---|
| Ruby, sapphire | 9 | Excellent for every day, including rings and bracelets. |
| Cubic zirconia | 8–8.5 | Handles daily wear well. |
| Topaz | 8 | Has cleavage — protect it from knocks. |
| Emerald | 7.5–8 | Brittle — wear with care and never clean it in an ultrasonic cleaner. |
| Rose quartz, amethyst, aventurine | about 7 | A good everyday choice; protect amethyst and rose quartz from long exposure to strong sun. |
| Agate, onyx, chalcedony | 6.5–7 | Very practical — they work in any kind of jewelry. |
| Labradorite | 6–6.5 | For everyday wear in moderation — it has distinct cleavage, so avoid knocks. |
| Opal (including synthetic) | 5.5–6.5 | Best in earrings and pendants; protect it from knocks, heat and chemicals. |
| Turquoise | 5–6 | Porous — take it off for handwashing, moisturizer and perfume; treat reconstructed turquoise the same way. |
| Lapis lazuli | 5–5.5 | Earrings and pendants; in rings, mostly for special occasions. |
| Malachite | 3.5–4 | Delicate and sensitive to acids — best in earrings and pendants. |
| Coral | 3–4 | Sensitive to sweat, perfume and acids — put it on after cosmetics. |
| Pearl, mother-of-pearl | 2.5–4.5 | Put it on last, wipe with a soft cloth, store separately. |
| Amber | 2–2.5 | Very soft — protect it from friction, alcohol and perfume. |
| 925 sterling silver (for comparison) | about 2.5–3 | Scratches easily; polishing restores the shine. |
Hardness also tells you how to care for your jewelry. The most important rule: harder scratches softer. If you toss a cubic zirconia ring, amber earrings and a silver chain into the same box, the zirconia will scratch both the amber and the silver. So:
Remember that 925 sterling silver itself is soft — about 2.5–3, less than most of the stones it holds. Fine scratches on silver are a natural sign of wear, and polishing brings back the shine. It’s also worth taking your jewelry to a jeweler now and then to check that the setting still holds the stone securely. You’ll find more advice in our guides on how to care for sterling silver jewelry and why you should take jewelry off for the pool and sauna, and about the alloy itself in our article on silver fineness.
Since 1984 — for more than 40 years — our family workshop in Rumia, Poland, has been making 925 sterling silver jewelry that is cast and then hand-finished: we set the stones by hand, grind and polish the silver and oxidize some designs. Our silver alloy is nickel-free. Our collection includes natural, reconstructed and synthetic stones, and we state the type of stone in each product description — which matters, because it affects how you should wear it. A synthetic stone has the same composition and structure as its natural counterpart, so it usually behaves in a similar way. A reconstructed stone is made from crushed stone bound together with a binder, so it’s best treated as a delicate stone. The opal in our collection is synthetic opal, our malachite and coral are reconstructed, and turquoise may be reconstructed. We explain the differences in our articles on how synthetic and reconstructed stones differ from natural ones and on synthetic vs natural opal.
For everyday wear, sterling silver rings with stones rated about 7 and above work best: with cubic zirconia, green agate, onyx, chalcedony or aventurine — and with labradorite, too, as long as you keep its cleavage in mind. Cubic zirconia is harder than most stones used in silver jewelry; we explain how it differs from a diamond in our article on diamond vs cubic zirconia — the key differences.
We recommend the more delicate stones — amber, pearls, mother-of-pearl, coral, malachite and turquoise — mainly in earrings and pendants, which rub against things less often. You’ll also find rings with these stones in our collection — just wear them mindfully: for going out and quiet days, not for gardening. Many of our stones are cut as cabochons, smooth and domed, with no sharp edges. Individual pieces may differ in small details, since every stone’s pattern and the hand finishing come out slightly different each time.
It lets you quickly compare which mineral is more resistant to scratching. A stone with a higher number will scratch a stone with a lower one, but not the other way around.
The hardest natural mineral is diamond — it rates 10 on the Mohs scale. It scratches every other mineral, although a hard knock on its edge can chip it.
Choose a stone with a hardness of about 7 or higher, such as agate, onyx, chalcedony, rose quartz or cubic zirconia. Amber, pearls, coral and malachite are better saved for going out or chosen in earrings.
Yes. Cubic zirconia rates about 8–8.5, so it’s harder than agate or amethyst and handles daily wear well. Clean it regularly, because grease and dust dull its sparkle.
Yes, because it’s soft — about 2.5–3. A silver polishing cloth will reduce fine dullness, and deeper scratches can be removed by a jeweler’s polishing.
It can. Hardness means resistance to scratches, not to impact. Stones with cleavage, such as topaz or labradorite, can crack after a hard knock, even if they rank high on the scale.
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