Frederick Mohs (1773-1839), a German mineralogist who devised a scale for determining the hardness of an unknown rock or mineral, which is often very useful in the identification process. This scale is a measure of a mineral's resistance to abrasion and is now known as the Mohs Scale of Hardness. The scale is defined by ten fairly common minerals (except for the diamond) of known hardness that are numerically ordered from the softest (1) to the hardest (10). Talc has a value of H=1, while the diamond has a value of H=10. The Mohs Scale of Hardness is based on the simple and observable fact that a harder material will scratch a softer one.