Mohs Hardness Scale

What the Mohs hardness scale measures

The Mohs hardness scale ranks a mineral's resistance to being scratched, from talc at 1 (the softest) to diamond at 10 (the hardest known natural material). Devised by the German mineralogist Friedrich Mohs in 1812, it is the standard shorthand jewelers and gemologists use to describe how well a gemstone resists surface wear. A mineral can scratch anything below it on the scale and is scratched by anything above it.

For jewelry, hardness matters because it predicts how a stone will keep its polish through years of wear. This is why sapphire and ruby, both a Mohs 9, and diamond at 10 are the classic choices for rings that are never taken off.

Which gemstones can I wear every day?

As a working rule, a stone at Mohs 8 or above is well suited to daily wear in a ring, including an engagement ring worn constantly. Diamond (10), sapphire and ruby (9), spinel and topaz (8) all hold their finish through ordinary life. Stones around Mohs 7 to 7.5 — aquamarine, tourmaline, garnet, amethyst and other quartz gems — wear well with a little care, ideally in protective settings. Below Mohs 7, a stone is more comfortable in earrings and pendants than in rings, where hands meet hard surfaces all day.

Hardness is not the same as toughness

An important distinction that the Mohs number alone does not capture: hardness resists scratching, while toughness resists chipping and breaking. Emerald is hard — Mohs 7.5 to 8 — yet it is relatively brittle and often included, so it needs a protective setting despite its high ranking. Jade, by contrast, is only Mohs 6.5 to 7 but is among the toughest gem materials known and resists breakage remarkably well. A complete durability picture considers hardness, toughness, and any cleavage planes together. When in doubt, ask a jeweler how a specific stone should be worn and cared for.

How to read the interactive scale

Each bead sits at the gemstone's typical Mohs value. Colour shows our everyday-wear guidance — deep sapphire for daily-wear stones through to wine for the most delicate. Use the wear filter to highlight only the stones that suit how you plan to wear a piece, switch to Compare Two to see which of two stones would scratch the other, or open the Full Chart for a sortable reference.

Mohs Hardness Scale FAQ

How hard is a sapphire on the Mohs scale?

Sapphire is a Mohs 9, second only to diamond and moissanite among gems commonly set in jewelry. That hardness, paired with excellent toughness, is why sapphire is an outstanding choice for an everyday ring and a durable alternative to diamond in engagement rings.

What is the hardest gemstone?

Diamond is the hardest, at Mohs 10 — the hardest known natural material. It is important to remember the Mohs scale is a ranking, not a linear measure: diamond is dramatically harder in absolute terms than corundum at 9, even though they sit just one step apart.

Is a higher Mohs number always better for jewelry?

Not on its own. A high Mohs number means a stone resists scratches, but jewelry durability also depends on toughness (resistance to chipping) and cleavage. Emerald ranks 7.5 to 8 yet is brittle, while jade ranks lower but is exceptionally tough. Consider all three properties, and the setting, when choosing a stone for daily wear.

Can I wear an opal or pearl ring every day?

These are among the softest gems in fine jewelry — opal at 5.5 to 6.5 and pearl at 2.5 to 4.5 — so they scratch and abrade easily. They are best enjoyed in earrings, pendants and occasional-wear rings, kept away from everyday knocks and household chemicals, and stored separately from harder pieces.

Methodology & sources

Hardness values follow standard gemological references, including the Gemological Institute of America (GIA) and the International Gem Society. Where a gemstone spans a range, the bead is plotted at a representative value and the range is noted in its detail. The Mohs scale is ordinal: the steps are not evenly spaced, so the gap between 9 and 10 is far larger in absolute hardness than the gap between, say, 5 and 6. We plot by Mohs rank and label the scale as a ranking rather than a linear measure to avoid overstating the differences.

Everyday-wear guidance combines hardness with gemological knowledge of a stone's toughness and cleavage, and is intended as general education. It is not a substitute for a jeweler's advice on a specific piece or setting.