The composition of zoisite is Ca2(Mg,Fe)5Si8O22(OH)2 and the crystals have a monoclinic crystal structure. The crystals are columnar with obvious longitudinal stripes. The aggregates are blocky, dense and columnar. The colour is white, grey, green, green-brown, pink, colourless, blue or purple. Zoisite has a transparent to translucent diaphaneity, a vitreous lustre, a specific gravity of 3.55, a Mohs hardness of 6.5–7, and uneven to conchoidal fractures. It is mainly found in shallow metamorphic rocks and hydrothermal alteration zones, and it is often a product of altered basic plagioclase. Transparent zoisite can be used as a gemstone.