The quality of resistance or property of minerals, gemstones, etc., which is determined by reference to an empirical scale of standard of minerals. Hardness is the resistance of a mineral offered to abrasion or scratching (scelerometric). The absolute hardness is determined with the aid of a sclerometer. Hardness varies according to crystallographic direction in certain minerals, such as cyanite or disthene three different hardness in three different crystallographic directions: 4.5, 6, and 7. The hardness of a gemstone can be determined using a hardness plate or hardness points. The general scale used as standard by mineralogist and gemologist called MohsТ scale.
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