Tanzanite is a member of the zoïsite family (like andalusite and thulite, for example). Until a few decades ago, zoïsites were associated with colors such as pale blue, green, brown, pink...sometimes even colorless. They were mainly used to make small sculptures. With the arrival of tanzanite in the family, another use for zoïsites was born, this stone being faceted and gem-quality. Tanzanite is a calcium-aluminium silicate that comes from veins in gneiss. In its rough state, it appears as a striated, multi-faceted prism. It owes its dominant blue color to a chemical element called vanadium. Its hardness is between 6 and 7, which means that lapidaries have to cut it very carefully to retain as much material as possible, while still revealing the most beautiful of colors. Without human intervention, tanzanite has brown hues.

It is common and accepted that most tanzanites are embellished by heating, which reveals their intense blue lustre.

As a result, the brown notes are greatly attenuated or even disappear. This process allows us to contemplate the gem in all its splendor, as different colors can be seen very distinctly in the same crystal, depending on the angle of view (this phenomenon is called pleochroism). Thus, from any given position, tanzanite can show us its most beautiful blue, or its pronounced shades of purple, violet...

The most popular tanzanites on the market are those with a very vivid blue or intense violet-blue to lavender color. There are imitations of this beautiful stone, given its fluctuating but growing success. As it comes from only one source in the world, supply does not always match demand. As a result, in the late 1990s, imitations began to appear. These include glass imitations and doublets with synthetic stones (such as synthetic fosterite).