Mohs scale of mineral hardness testing the resilience of certain flat panel display components (such as cover glass for LCDs or encapsulation for OLEDs). The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly. The samples of matter used by Mohs are all different minerals. Minerals are chemically pure solids found in nature. Rocks are made up of one or more minerals. As the hardest known naturally occurring substance when the scale was designed, diamonds are at the top of the scale. The hardness of a material is measured against the scale by
Carbonate hardness [milli[equivalent]s] per litre (meq/L) or ppm. Carbonate hardness expressed in ppm does not necessarily equal carbonate alkalinity expressed in ppm. formula_1 whereas formula_2 However, for water with a pH below 8.5, the CO will be less than 1% of the HCO so carbonate alkalinity will equal carbonate hardness to within an error of less than 1%. In a solution where only CO affects the pH, carbonate hardness can be used to calculate the concentration of dissolved CO in the solution with the formula CO = 3 × KH × 10, where KH is degrees of carbonate hardness and CO is