Mohs Hardness Scale
The Mohs hardness scale is one way in which the hardness of a material is represented numerically. Hardness is the resistance of a material to indentation and is measured by the permanent depth of an indentation that has occurred. The Mohs hardness scale rates the hardness of material from 1 to 10 using the ability of another material to scratch the test material. Typically used in geological contexts, the Mohs hardness scale ranges from talc to gypsum to calcite, to fluorite, to apatite, to feldspar, to quartz, to topaz, to corundum, to diamond.