Hardness often is measured on the (nonlinear) Mohs Scale, which associates a hardness number to each mineral, from 1 (softest) to 10 (hardest): Talc Gypsum Calcite Fluorite Apatite Orthoclase Quartz Topaz Corundum Diamond As a comparison, a fingernail has hardness 2.5, glass has hardness 5.5, and a steel file has hardness 6.5.
(Hardness; is measured; on the (nonlinear) Mohs Scale, which associates a hardness number to each mineral, from 1 (softest) to 10 (hardest): Talc Gypsum Calcite Fluorite Apatite Orthoclase Quartz Topaz Corundum Diamond; T:often) (the (nonlinear) Mohs Scale; associates; a hardness number; to each mineral) (a fingernail; has; hardness 2.5) (glass; has; hardness 5.5) (a steel file; has; hardness 6.5)
Hardness the (nonlinear) Mohs Scale a fingernail glass a steel file
is measured associates has has has
on the (nonlinear) Mohs Scale, which associates a hardness number to each mineral, from 1 (softest) to 10 (hardest): Talc Gypsum Calcite Fluorite Apatite Orthoclase Quartz Topaz Corundum Diamond T:often
a hardness number to each mineral
hardness 2.5
hardness 5.5
hardness 6.5