Mineral necessarily constant for all sides, which is a function of its structure; crystallographic weakness renders some directions softer than others. An example of this property exists in kyanite, which has a Mohs hardness of 5½ parallel to [001] but 7 parallel to [100]. The most common scale of measurement is the ordinal Mohs hardness scale. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc, a phyllosilicate, to diamond, a carbon polymorph that is the hardest natural material. The scale is provided below: Lustre indicates how light reflects from the mineral's
Zoisite 6 and 7 on the Mohs hardness scale, and its specific gravity ranges from 3.10 to 3.38, depending on the variety. It streaks white and is said to be brittle. Clinozoisite is a more common monoclinic polymorph of CaAl(SiO)(SiO)O(OH). Transparent material is fashioned into gemstones while translucent-to-opaque material is usually carved. The mineral was described by Abraham Gottlob Werner in 1805. He named it after the Carniolan naturalist Sigmund Zois, who sent him its specimens from Saualpe in Carinthia. Zois realized that this was an unknown mineral when it was brought to him by a mineral dealer, presumed to be