What on Earth Is Tanzanite?

Tanzanite is the purplish-blue variety of the mineral zoisite, found only in the Merelani Hills of northern Tanzania. It shows different colours from different angles (pleochroism), rates 6.5 on the Mohs scale and is a December birthstone, so it suits rings, pendants and earrings best with a little care. This guide covers its properties, history and lore.

The Physical Properties of Tanzanite

Tanzanite is a vitreous stone with amazingly high clarity. This transparent stone has a Mohs hardness value of 6.5 which means it is soft enough to get scratched when worn on a daily basis (i.e. as a ring). It is advisable to not wear it during activities where it can be exposed to high impact or abrasion.

Tanzanite comes in a range of blue hues: a very light blue, vivid blue, purplish blue, to violetish blue. Specimens with a stronger tone and saturation are the most valuable ones in the market. Tanzanite's blueness is produced by the stone's vanadium content.

Heating zoisite to 600 °C for 30 minutes changes the oxidation state of vanadium. This turns the blue colour of the stone to a darker shade.

This stone has pleochroic qualities which makes it appear in different colours when viewed from different angles. Some stones can look blue from one direction and look violetish blue from other directions.

The History of Tanzanite

It was Tiffany & Co., an American luxury jewelry giant that used the name tanzanite to describe blue zoisite. The stones were named after the known producer of commercial blue zoisite, in northern Tanzania.

Today, tanzanite stones can only be found in the Merelani Hills in Arusha Region, Africa. The production of tanzanite is limited in this locality, making it rare and limited in supply.

The first commercially available tanzanite had been faceted in 1967. At that time, jewelers had not heard of the gem. So Tiffany & Co. mounted a public education program to raise awareness on the value of these blue Zoisite stones.

As it rose to popularity, tanzanite was named as a new birthstone for December by the American Gem Trade Association (AGTA).

The Lore of Tanzanite

Legend has it that Maasai cattle herders were the first to discover the blue zoisite in 1967, according to the Gem Institute of America (GIA). It was after a fire caused by lightning razed some areas in Merelani.

The herders noticed that brown zoisite crystals turned into deep blue stones after being exposed to fire.

The Maasai are said to have seen tanzanite as a spiritual stone linked with calmness and compassion.

The Metaphysical Properties of Tanzanite

In crystal lore, tanzanite is a symbol of intuition and a wider perspective. It is also a favourite simply for its violet-blue colour.

Many people find its deep blue calming to look at, and it is often chosen as a keepsake for a milestone.

Others see the way tanzanite goes through intense heat before it reaches its shade and sheen as a symbol of personal growth, and wear it as a reminder to stay true to themselves.