This Mineral Identification Kit for Hardness and Streak Testing contains minerals with a Mohs hardness of 1 to 9: a streak plate: and instructions about the Mohs Scale, which measures mineral hardness by the scratch resistance of various minerals through the ability of a harder material scratching a softer material. 'Mohs scale of mineral hardness' was created in 1812 by the German mineralogist, Friedrich Mohs.