Mohs hardness scale. Array of common objects and substances with labels indicating their hardness on the Mohs scale of hardness. This scale from 1-10 normally applies to minerals, ranging from talc (1) to diamond (10), with successive minerals able to scratch samples of minerals below them on the scale. This scale includes fingernails (2) and two metals, bronze (3, the two pence coin) and steel (6, screw-thread bolt). After 1992, two pence coins were copper-plated steel, though copper has around the same hardness as bronze.
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