Mohs scale of mineral hardness 77 AD. While greatly facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting. Despite its lack of precision, the Mohs scale is highly relevant for field geologists, who use the scale to roughly identify minerals using scratch kits. The Mohs scale hardness of minerals can be commonly found in reference sheets. Mohs hardness is useful in milling. It allows assessment of which kind of mill will best reduce a given product whose hardness is known. The scale is also in use at digital electronic manufacturers, for
Carbonate hardness given in ppm. The term "carbonate hardness" is also sometimes used as a synonym for temporary hardness, in which case it refers to that portion of hard water that can be removed by processes such as boiling or lime softening, and then separation of water from the resulting precipitate. Carbonate hardness Carbonate hardness, is a measure of the water hardness caused by the presence of carbonate () and bicarbonate () anions. Carbonate hardness is usually expressed either in degrees KH (dKH) (from the German ""Karbonathärte""), or in "parts per million calcium carbonate" ( ppm or grams per litre|mg/l). One dKH