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There are several ways to test material hardness. One of the most accessible is a 203 year old scale created by the 19th century German geologist Friedrich Mohs, which compares the scratch resistance of minerals relative to one another. The Mohs scale, as it is known, uses 10 minerals of increasing hardness as reference points. It rates talc as 1 and goes all the way up to diamond at a 10 rating. (You can see a chart of the scale, below.) The idea is that each mineral on the scale can scratch every mineral ranked below it. Consumer Reports has a Mohs hardness kit that we use in our test labs. It contains a series of picks to represent each level of the Mohs scale.