Here’s a rather random, but nevertheless interesting, science fact : Did you know that there’s a Scientific scale of hardness ?

We should point out that it’s not some sort of machismo ranking of scientists – as if Albert “Mad Dog” Einstein was any much a bigger ‘bad a$$’ than Isaac “Iron man” Newton!. It’s actually a scale of the hardness of solids. And when you see it you’ll find that its surprisingly simple – no equations, no calculus and no test tubes involved at all.

The Relative Hardness of Being*

Devised by the German geologist Friedrich Mohs (1773- 1839), the Mohs scale of mineral hardness arranges 10 minerals in an order of increasing hardness, the difference being that a mineral on the list can be scratched by any below it – Simples!
(*with apologies to Milan Kundera author of “The Unbearable Lightness of Being”)

Mohs HardnessMineral
1(softest) Talc
10 (hardest)Diamond

Extending the Scale

The scale does not simply apply to these 10 minerals – it can be used to assess the hardness of any solid. So, if we take the minerals listed above, if a solid can be scratched by apatite but not fluorite then its Mohs hardness is between 4 and 5.

Graphite (found in pencil lead) has a Mohs hardness of between 1 and 2. Anything up to 2.5 can typically be scratched by a fingernail, up to 4 by a coin and up to 6 by a knife. The scale is a relative one – the difference in absolute hardness between each mineral isn’t consistent.