Zoisite vs. Tanzanite — What's the Difference?

Zoisite, first known as saualpite, after its type locality, is a calcium aluminium hydroxy sorosilicate belonging to the epidote group of minerals. Its chemical formula is Ca2Al3(SiO4)(Si2O7)O(OH).

Tanzanite is the blue and violet variety of the mineral zoisite (a calcium aluminium hydroxyl sorosilicate), caused by small amounts of vanadium. Tanzanite belongs to the epidote mineral group.

A gray, brown, pink, green, or blue mineral, Ca2Al3(SiO4)3(OH), used in ornamental stonework and as a gemstone.

A transparent variety of zoisite, used as a gem.

(mineral) A mineral with orthorhombic crystals, Ca₂Al₃(SiO₄)(Si₂O₇)O(OH).

A trichroic violet-blue variety of the mineral zoisite mined in Tanzania, used as a gemstone.

A grayish or whitish mineral occurring in orthorhombic, prismatic crystals, also in columnar masses. It is a silicate of alumina and lime, and is allied to epidote.