Zoisite, originally called Saualpite, derives its name from the Slovenian mineralogist Sigmund Zois who recognized it as an unknown mineral. Zoisite was first discovered in the Sau-Alp mountains in Austria (hence the name Saualpite) in 1805, by the mineral dealer Simon Prešern.

Zoisite is of a calcium aluminum silicate chemical composition. It has a hardness of 6.5 to 7 on the Mohs scale.

When found in crystal form, Zoisite has a high refractive index of: 1.685 to 1.707. It also has a strong Pleochroism (which is the optical phenomenon where a gemstone displays different colors when observed at different angles, especially with polarized light.)

Chatoyancy in Zoisite is rare.

Zoisite comes in green, brown, red-violet, bluish-green and pink colors. It has a perfect cleavage. Zoisite is opaque. May be translucent in thin backlit sections. It has a glass-like luster. Zoisite occurs with Fingerprint-like, (black) graphite and (hexagonal) hematite inclusions.

Zoisite becomes important due to the fact that another variety of Zoisite was discovered in 1967 in Tanzania, which today is one of the most sought-after gemstones of our time: Tanzanite. Tanzanite is the transparent blue to purplish-blue gemstone-quality Zoisite specimen.

The other members of the Zoisite species are Thulite and Anyolite.

Thulite was first discovered in 1820 in Norway and its name is derived from the mythical island of Thule.

Thulite is the pink to red manganese-rich variety of Zoisite. Thulite can be confused with Rhodonite. (Worth noting: the purple Tanzanite and green variety and Ruby Zoisite are all unique gemstones). Thulite as a gemstone is usually polished into cabochons and beads and carved into ornamental figures.

The name Anyolite is derived from the Masai word for green which is ANYOLI. It was first discovered in Longido, Tanzania in 1954. It is composed of intergrown green Zoisite with black hornblende and Ruby. It is usually called Ruby Zoisite because its main characteristics is this beautiful contrast between green Zoisite and red Ruby. Ruby Zoisite, like Thulite is a minor Zoisite gemstone and is polished into cabochons and beads and carved into ornamental figures. The red Ruby in green Zoisite is opaque and of low quality.

Tanzanite is a rare Zoisite crystal. It is 1000 times rarer than diamonds. It was first discovered by Maasai herdsmen in Tanzania in 1967 who after such discovery, took specimens to Manuel de Sousa, a local amateur gemologist who first thought they had given him blue Sapphires, but after the identification procedure it was revealed that what he had in his hands was the rare Zoisite crystals.

Tanzanite comes in a variety of blue colors, from lovely sky blue to deep midnight blue with some flashes of red and touches of violet and purple. It also comes in a one-of-a-kind purple color. Tanzanite is transparent high-quality gemstone which is faceted into a variety of gemstone cuts.

Thulite and Anyolite (Ruby Zoisite) are not treated or enhanced in anyway but come in their natural colors. Tanzanite, on the other hand, is heat treated to achieve its beautiful blue color.

Tanzanite deposits can only be found in the Merelani Hills of Arusha, Tanzania.
Green Zoisite and Ruby Zoisite also can only be found in Longido, Tanzania.
Pink Thulite deposits are found in Norway, Australia, Namibia, and North Carolina, in the United States.