Moh''s Scale of Hardness Marblecare Ltd.
The Moh''s Hardness scale is not a linear scale unlike the scale of absolute hardness. So Orthoclase at 6 is not twice as hard as Calcite at 3, nor is the difference between talc and gypsum the same as the difference between Corundum and Diamond. An absolute hardness scale gives a clearer idea of how hard the minerals are in relation to each other.