Mohs Hardness Scale
1–10 Mohs hardness reference for minerals.
Overview
The Mohs Hardness Scale reference lists the ten reference minerals that define the scale, from talc at 1 (softest, can be scratched with a fingernail) to diamond at 10 (the hardest naturally occurring mineral). Each row includes the mineral name, the Mohs number, a typical absolute hardness value in Vickers and a note on a familiar reference object — fingernail, copper coin, steel knife.
The tool is for geology students learning mineral ID in the field, jewellers explaining stone durability to customers and anyone curious whether their countertop will scratch. Long-tail queries it covers include "Mohs hardness of quartz", "is diamond really the hardest mineral", "what is Mohs scale used for" and "mineral hardness vs Vickers".
How it works
The Mohs scale is ordinal, not linear. Each step up means the mineral can scratch all the lower-numbered minerals, but the absolute difference in hardness grows rapidly: corundum (9) is only one Mohs step harder than topaz (8) but is roughly twice as hard in absolute terms; diamond (10) is roughly four times harder than corundum.
The reference shows both the Mohs number and the approximate Vickers hardness so you can see how non-linear the scale is. Common reference objects are tabulated: a fingernail is about 2.5, a copper coin is around 3.5, a steel knife around 5.5 and a streak plate around 7.
Examples
Talc → 1 → ~1 HV → scratched by fingernail (2.5)
Calcite → 3 → ~110 HV → scratched by copper coin
Quartz → 7 → ~1100 HV → scratches glass and steel
Diamond → 10 → ~10000 HV→ hardest natural mineral
FAQ
Why is the Mohs scale not linear?
It was designed as a relative ranking in 1812, when no absolute hardness measurement existed. Each step was chosen so the higher mineral scratches the lower, with no attempt at evenly spaced values. The non-linearity becomes obvious once Vickers measurements are layered on.
Can a mineral be a non-integer Mohs hardness?
Yes. A mineral that scratches calcite (3) but is scratched by fluorite (4) is approximately Mohs 3.5. Field hardness kits include intermediate fractional values.
Why is diamond not unscratchable?
Diamond is the hardest natural mineral, but it can be scratched by another diamond and by some synthetic materials like cubic boron nitride. It's also relatively brittle — hardness is resistance to scratching, not to chipping or shattering.
How does Mohs relate to Vickers and Knoop?
Vickers and Knoop are absolute hardness measurements that press a calibrated indenter and measure the resulting dent. They give precise numbers but require lab equipment. Mohs is a field-friendly relative ranking.
Is the scale still used by geologists?
Yes, every day. It is fast, requires only a few reference samples, and is enough to ID most minerals when combined with colour, streak and crystal habit.