Mohs Scale was developed in 1812 by German mineralogist Friedrich Mohs (1773-1839)
Mohs Scale of hardness is a RELATIVE scale, not proportional. I mean by this that a mineral with the hardness of 8 will NOT be twice as hard as a 4. (For example, diamond is 4X harder than sapphire!).
It is really a scale of relative "scratchability".
#1 is softest..................#10 is hardest