While most people have long known that diamonds are the hardest mineral on earth, talc is the softest mineral. According to the Mohs scale, which determines hardness from a range of 1 to 10, talc is a one. It also ranks as an absolute hardness of one. Diamonds are a ten on the Mohs scale, with an absolute hardness of 1600.
     Friedrich Mohs, a mineralogist, developed the Mohs scale of hardness in 1812, determined by which material is harder by its ability to scratch another mineral.
The absolute hardness scale is not as popular as Mohs but offers a proportional range for mineral comparison. For example, Mohs offers talc as one and calcite as a three, while absolute hardness scale measures talc as one and calcite as a nine.
     By the way, diamonds are no longer the hardest material on earth. Scientists have discovered that wurtzite boron nitride and lonsdaleite are both materials harder than a diamond.