Mohs Hardness Scale Explained: All 10 Minerals, Ranked

What Is the Mohs Hardness Scale?

The Mohs hardness scale is a 1-to-10 ranking of mineral hardness — a mineral's resistance to being scratched. Devised in 1812 by the German mineralogist Friedrich Mohs, it orders ten reference minerals from talc (1, the softest) to diamond (10, the hardest). Each mineral on the scale can scratch every mineral below it and can be scratched by every mineral above it. That's the whole system: no lab equipment, no formulas, just the simple question "what scratches what?"

Two centuries later, it's still the standard shorthand geologists, gemologists, and jewelers use every day. When someone says "sapphire is a 9," they're speaking Mohs.

One thing worth being precise about, because it's commonly garbled online: hardness means scratch resistance, not durability or strength. A diamond is the hardest natural material known, yet it can still chip or cleave if struck at the wrong angle. Hardness and toughness are different properties — more on that below.

All 10 Mohs Minerals, Ranked from Softest to Hardest

Here is the full scale, with the everyday comparison that makes each number meaningful.

The 10 reference minerals, briefly

• Talc (1) — the softest mineral on the scale, familiar as the main ingredient in talcum powder. You can scratch it with a fingernail without trying.
• Gypsum (2) — the mineral behind plaster and drywall. Still soft enough for a fingernail to mark.
• Calcite (3) — the calcium carbonate that builds limestone and marble. A copper coin will scratch it.
• Fluorite (4) — a beautifully colorful collector's mineral, but far too soft for everyday jewelry.
• Apatite (5) — a calcium phosphate mineral; chemically, it's a close cousin of the material in your teeth and bones.
• Orthoclase feldspar (6) — feldspar is the most abundant mineral group in Earth's crust. This marks the point where minerals begin to scratch window glass.
• Quartz (7) — the great dividing line of the scale, and the hardness benchmark that matters most in daily life (see why below).
• Topaz (8) — a genuine gemstone in its own right and the scale's step above quartz.
• Corundum (9) — aluminum oxide. When it's red, we call it ruby; other colors are sapphire. Second only to diamond.
• Diamond (10) — pure crystallized carbon and the hardest naturally occurring material known. Nothing in nature scratches a diamond except another diamond.

What the Numbers Actually Mean (and Don't)

It's a ranking, not a measurement

The Mohs scale is ordinal: it tells you the order of hardness, not the size of the gaps. Those gaps are wildly uneven. Measured on absolute instruments-based hardness tests, the jump from corundum (9) to diamond (10) is several times larger than the jump from talc (1) all the way to corundum (9) put together. Diamond isn't "one step" harder than sapphire — it's in a different league entirely.

So treat Mohs numbers the way they were designed to be used: as a practical ranking for comparing minerals, not as a linear measurement.

Hardness is not toughness

This distinction saves jewelry:

• Hardness = resistance to scratching (what Mohs measures).
• Toughness = resistance to chipping, cracking, and breaking.

Diamond is supremely hard but only moderately tough — it has cleavage planes and can chip from a sharp knock. Jadeite, by contrast, sits at only about 6.5–7 on the Mohs scale yet is exceptionally tough, which is why it can be carved into thin, durable bangles. A stone can be hard but brittle, or soft but tough.

Half steps are normal

Real-world minerals rarely land exactly on the reference points, so gemologists use half values freely: garnet at 6.5–7.5, beryl at 7.5–8, chrysoberyl at 8.5. The in-between numbers simply mean "scratches the mineral below, scratched by the mineral above."

Where Does Quartz Fall on the Mohs Scale — and Why 7 Is the Magic Number

Quartz sits at 7, and that single fact does more practical work than the rest of the scale combined.

Quartz is one of the most abundant minerals in Earth's crust, which means ordinary dust and grit are loaded with microscopic quartz particles. Every time you wipe a surface — or a gemstone — you're effectively dragging fine quartz sandpaper across it.

The consequence:

• Stones harder than 7 (topaz, spinel, corundum, diamond) shrug off everyday dust and stay polished for decades.
• Stones at 7 (amethyst, citrine, and other quartz gems) hold up well with reasonable care.
• Stones softer than 7 (opal, moonstone, turquoise, pearl) will slowly accumulate fine scratches from nothing more than daily wear and careless cleaning.

This is why jewelers steer people toward sapphire or diamond for engagement rings worn daily, and why soft stones belong in earrings and pendants that lead gentler lives. It's also the logic behind stone-specific cleaning advice — our guide to cleaning gemstone jewelry safely leans on Mohs hardness constantly.

What Is the Hardest Mineral?

Diamond is the hardest naturally occurring mineral, holding the 10 spot on the Mohs scale. It is pure carbon whose atoms are locked in a rigid three-dimensional lattice, and no other natural material can scratch it. That extreme hardness is why the majority of industrial diamonds end up in cutting, grinding, and drilling tools rather than jewelry.

Two honest footnotes:

• Synthetic materials can compete. Lab-created substances such as certain forms of boron nitride rival or exceed diamond in specific hardness tests — but among natural minerals, diamond stands alone.
• Hardest doesn't mean indestructible. Diamond's cleavage planes mean a hard blow at the wrong angle can chip it. Hard, yes; invincible, no.

At the other extreme, talc is the softest mineral on the scale — soft enough to crumble between your fingers.

Mohs Hardness of Common Gemstones

The ten reference minerals are only the skeleton of the scale. Here's where the gems people actually own tend to fall. Ranges reflect natural variation between specimens.

*A note of honesty on that asterisk: hardness isn't the whole durability story. Most emeralds on the market are fracture-filled with oils or resins to improve their appearance — a standard, widely practiced treatment — and those fillers, not the beryl itself, are the fragile part. Likewise, most sapphires and rubies are heat-treated to improve color; heating doesn't reduce their hardness, but it's a fact any honest seller should disclose. Treatment status matters as much as the Mohs number when deciding how to wear and clean a stone.

If you're matching a stone to a month rather than to a hardness chart, our birthstones by month guide covers all twelve — including which birthstones need the most protection.

How to Do a Scratch Test (Carefully)

Hardness testing is a classic field-identification technique, and you can approximate it at home with common objects:

1. Fingernail — about 2.5. Scratches talc and gypsum.
2. Copper coin — about 3. Scratches calcite.
3. Steel knife or window glass — about 5.5. Scratches apatite; won't scratch feldspar.
4. Steel file — about 6.5. Scratches feldspar; struggles against quartz.
5. Quartz crystal — 7. The most useful single reference a collector can own.

Work upward from soft to hard, use an inconspicuous spot, and press lightly — you're looking for a genuine groove, not a powdery streak that wipes away (that's often just the softer testing tool leaving residue).

Two firm cautions. First, a scratch test is destructive by nature: never use it on finished jewelry, polished specimens, or any stone you care about. Second, hardness alone rarely identifies a mineral — plenty of very different minerals share the same hardness. Treat it as one clue among several; our walkthrough of gemstone identification tests you can do at home shows how hardness fits alongside streak, luster, and other observations.

Why a 200-Year-Old Scale Still Matters

The Mohs scale has survived every laboratory refinement since 1812 for one reason: it answers the question people actually have. Nobody shopping for a ring needs a stone's indentation hardness in kilograms-force per square millimeter — they need to know whether it will scratch in a drawer next to their other jewelry. (Answer: if it's softer, yes. Store stones separately.)

Learn the ten minerals, remember that quartz at 7 is the threshold for everyday durability, and keep hardness separate from toughness in your head. With those three ideas, most of the practical decisions about wearing, storing, and cleaning gemstones fall into place on their own.