The resistance of a mineral or metal to scratching, indentation, abrasion, or cutting. There are scales and tests of hardness, including the Mohs scale using specific minerals numbered in order of hardness with which other substances are compared. There is also the diamond pyramid scale and the Brinell hardness scale. The Brinell method involves the forcing of a ball of hardened steel of known diameter into the sample to be tested, for a standard length of time under standard pressure. The softer the metal under test, the greater the diameter of the resulting depression, which is measured with a micrometer. Such tests allow conclusions to be drawn about past metalworking techniques and their efficiency. There are more than 30 different hardness tests.