A silicate mineral, zoisite has the complex chemical formula of Ca2Al3(SiO4)(Si2O7)O(OH). Its crystal structure is orthorhombic, but it has a polymorph, known as clinozoisite, with the same composition and a monoclinic crystal structure. This mineral can be a variety of colors, including blue, green, pink, yellow, or colorless, and has a Mohs hardness of 6.5
Zoisite is typically only found in small quantities and therefore not used by industry, but there are a variety of well-known zoisite minerals. Tanzanite is a blue or violet variety of this mineral, caused by the addition of small amounts of vanadium. Thulite, meanwhile, is a pink variety, of which the color is created when manganese substitutes for calcium in the crystal structure. Both of these variations are considered rare.
Occasionally, zoisite also occurs alongside crystals of ruby in the form of a mineral known as anyolite or ruby-in-zoisite. The zoisite in these occasions is green in color, with sections of pink or red from the ruby.