Birthstone Feature: Zoisite’s Famous Blue-Violet Variety Was Discovered in 1967

While zoisite has been known to gemologists since 1805, its most famous blue-violet variety was discovered in 1967 along the foothills of Mount Kilimanjaro in Tanzania by a Maasai tribesman named Jumanne Ngoma.

Ngoma revealed his find to a prospector named Manuel d’Souza, who had the sapphire-like specimens analyzed by the Gemological Institute of America. The results revealed the intense, electric blue gems were a never-before-seen variety of zoisite.

In less than a year, the marketing team at Tiffany was preparing a broad-based advertising campaign to introduce the unique gem to the world — but one large hurdle stood in the way.

Zoisite, pronounced “zow-uh-site,” sounded a little too much like “suicide,” so the gem was cleverly rebranded as “tanzanite” to honor its country of origin.

The original campaign advertised that tanzanite could now be found in two places — “in Tanzania and at Tiffany’s.” It was wildly successful and tanzanite soon became a household name.

In 2002, the American Gem Trade Association added tanzanite to the jewelry industry’s official birthstone list. Tanzanite joined turquoise and zircon as the official birthstones for December.

Interestingly, while other varieties of zoisite — in a range of colors from pink, brown and yellow to green, grey and colorless — are found in Kenya, Norway, Switzerland, Austria, India, Pakistan and the US, the vibrant blue-violet crystals are mined in only one location on earth. The area in Merelani Hills near Arusha, Tanzania, measures just 2km wide by 4km long, and the remaining lifespan of the mine is said to be less than 30 years.

The half-carat zoisite specimens seen in the photo, above, reside in the Smithsonian in Washington, DC, and were gifted to the National Gem Collection by Edward W. Boehm in 2008.

The Smithsonian’s website explains that tanzanite exhibits the optical phenomenon of pleochroism, appearing intense blue, violet or red, depending on the direction through which the crystal is viewed.

In 2018, Asha Ngoma, the daughter of Jumanne, made a desperate plea to then-Tanzanian President John Magufuli on behalf of her nearly 80-year-old dad, who was ill, partially paralyzed and struggling financially. The President responded in April of that same year with a reward of 100 million shillings (about $44,000) and well-deserved words of praise.

“Mr. Ngoma is a veritable Tanzanian hero,” Magufuli told The Citizen.

The man credited with the discovery of tanzanite passed away less than a year later in January of 2019.

Credit: Photo by Greg Polley / Smithstonian.