the German geologist Friedrich Mohs (1773-1839) invented this scale in 1812. Ten minerals arranged and numbered from the softest to the hardest. The mineral with a higher number can scratch a lower-numbered mineral, but not the other way around. The series is: 1-talc, 2-gypsum, 3-calcit, 4-fluorite, 5-apatite, 6-orthoclase, 7-quartz, 8-topaz, 9-corundum, 10-diamond.