Zoisite
Zoisite belongs to the silicate group. It contains calcium, aluminum, and silicon. Its chemical formula is Ca₂ (AlOH) Al₂ ( SiO₄ ) ₃ . It occurs in massive forms or as striated prismatic crystals. Zoisite is found in green or white. It is called thulite when pink and tanzanite when blue. This mineral is sometimes associated with ruby and pargasite, in which it may contain numerous inclusions. The hardness of zoisite varies between 6 and 7/10 on the Mohs scale (10 for diamond), and its average density is 3.3 (1 for water). The streak on porcelain is white. The name zoisite comes from the name of the Austrian naturalist S. Zois.
