How to determine the hardness of a mineral?

The hardness of a mineral can be determined by using the Mohs scale of hardness, which ranks minerals from 1 (softest) to 10 (hardest). This scale is based on the ability of one mineral to scratch another. By testing the mineral's resistance to scratching with common objects of known hardness, such as a fingernail (2.5), a copper penny (3.5), a steel nail (5.5), and a glass plate (5.5), you can determine its hardness level.