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
Ringelmann scale Ringelmann scale The Ringelmann scale is a scale for measuring the apparent density or opacity of Smoke. It was developed by a French professor of agricultural engineering Maximilien Ringelmann of La Station d'Essais de Machines in Paris in 1888. Ringelmann also discovered what is now called the Ringelmann effect. The scale is has a 5 levels of density inferred from a grid of black lines on a white surface which, if viewed from a distance, merge into known shades of grey. Shade 1 is slightly grey and is usually categorized by air pollution boards as acceptable. It corresponds to an