What is the Mohs hardness scale?

The Mohs scale is a relative measure of mineral scratch resistance, ranging from 1 (talc, the softest) to 10 (diamond, the hardest). It was created by German mineralogist Friedrich Mohs in 1812. A mineral with a higher Mohs number can scratch any mineral with a lower number.

Is the Mohs scale linear?

No. The scale is ordinal, not linear. The actual hardness difference between levels is not equal — for example, diamond (10) is roughly 4 times harder than corundum (9) in absolute terms, even though they are only one step apart on the Mohs scale.

How do you test hardness in the field?

Scratch the unknown mineral against a reference material. If your fingernail (Mohs ~2.5) scratches the mineral, it is softer than 2.5. A copper coin (~3.5), steel knife blade (~5.5), and glass plate (~5.5–6) are handy field references.

What common minerals have a Mohs hardness of 7?

Quartz is the standard mineral at Mohs 7. Many gemstones — including amethyst, citrine, and agate — are varieties of quartz and share the same hardness. Steel files also scratch at about 7, making quartz a useful dividing line.

Why is hardness important for gemstones?

Harder gemstones resist daily abrasion from dust (which is mostly quartz, Mohs 7). Gems below 7 (opal, pearl, fluorite) scratch more easily and require extra care. Diamond (10), corundum/ruby/sapphire (9), and topaz (8) are popular for jewelry partly because of their high hardness.

Mineral Hardness Reference

Browse or search the complete Mohs hardness scale — all 10 levels, common minerals at each level, scratch tests, and everyday hardness comparisons.

Filter level:

Showing all minerals across 10 hardness levels.

Mohs	Mineral(s)	Scratch Test	Everyday Comparison	Crystal System

Visual Hardness Scale

Talc

Gypsum

Calcite

Fluorite

Apatite

Orthoclase

Quartz

Topaz

Corundum

Diamond

Each level can scratch all minerals below it. Note: the scale is ordinal, not linear — diamond is ~4x harder than corundum in absolute terms.

Field Test Tools

Fingernail~2.5
Copper coin~3.5
Glass plate~5.5
Steel knife blade~5.5
Steel file~6.5
Hardened steel~7–8

Gemstone Hardness

Pearl / Opal2.5–6.5
Turquoise5–6
Amethyst / Agate7
Spinel8
Ruby / Sapphire9
Diamond10

Industrial Uses

Talc (filler, cosmetics)1
Gypsum (plaster)2
Apatite (fertilizer)5
Quartz (glass, electronics)7
Corundum (abrasives)9
Diamond (cutting tools)10

Summary

The Mohs hardness scale ranks minerals from 1 (softest, talc) to 10 (hardest, diamond) based on their resistance to scratching. Developed by Friedrich Mohs in 1812, it remains the standard field test for identifying minerals. This reference lists every Mohs level with representative minerals, common scratch tests, and everyday objects for comparison.

How it works

Use the search box to filter minerals by name or hardness number.
Browse the table sorted by Mohs hardness level (1 to 10).
The "Scratch Test" column shows what each mineral can and cannot scratch.
The "Everyday Comparison" column links hardness to familiar objects.
Click any row to expand additional details about that mineral or level.

Use cases

Identify unknown minerals in the field using scratch tests.
Study for geology, earth science, or mineralogy exams.
Compare mineral hardness to understand gemstone durability.
Teach students about material properties and the Mohs scale.
Select minerals or gemstones for jewelry based on scratch resistance.
Understand why diamond is used in cutting and drilling tools.

Frequently Asked Questions

Last updated: 2026-05-28 · Reviewed by Nham Vu