The hardness scale is a system used to measure the resistance of materials to scratching or indentation. One of the most well-known scales is the Mohs scale, which ranks minerals from 1 to 10 based on their hardness. For example, talc is rated as 1, while diamond, the hardest known natural material, is rated as 10. In addition to the Mohs scale, there are other hardness tests, such as the Brinell and Rockwell tests, which are used for metals and other materials. These tests provide numerical values that help in comparing the hardness of different substances, aiding in material selection for various applications.