Rapaport Magazine
Colored Gemstone

Onsite in Tanzania

Photographs by Bill Kalina

By Deborah Yonick

Discovered in 1967, tanzanite is mined in one place on the planet — in the foothills of Mount Kilimanjaro, Tanzania, in a deposit created more than 500 million years ago as Africa’s Rift Valley was forming. The velvety blue crystals, originally thought to be sapphire, were later identified as blue zoisite. Early on, the gemstone caught the eye of Henry Platt, Tiffany & Co. president, who named the gem and launched the extensive marketing campaign that established tanzanite as the iconic gem that it is today.

Tanzanite is mined deep underground from complex folds in the rock of a 2.7-square-mile site, approximately 30 miles from the trading hub of Arusha. This sliver of earth is divided into four blocks. Small-scale and artisanal miners operate in three of them, while TanzaniteOne Mining, a wholly owned subsidiary of Richland Resources Ltd., runs a large-scale mining operation in the largest block. The company has been involved in the area since 2004, three years after tanzanite mine development began there.

While the United States remains the largest consumer of tanzanite, China, India and other emerging markets are expected to be the next big distribution channel for this gem. Unlike ruby, emerald and sapphire, which have long histories and multiple sources, tanzanite’s time on earth is finite as geological research suggests only another 30 years of material is left in the ground.

Tanzania’s mining sector contributes 2.3 percent of the country’s gross domestic product (GDP) but it is projected to be 10 percent in 13 years, reports the government’s Development Vision 2025. As part of the gemstone corridor extending from northern Mozambique to central Kenya, the area where tanzanite is currently being mined is the most important gem mining area in the country, with as many as 70,000 people supported by the mining, cutting and trading operations.

The work zones closest to the surface extend down three-tenths of a mile, which took a decade to reach, says TanzaniteOne’s Mine Manager Damien Masala, pictured at left at the entrance to the company’s Main Shaft, which descends on a one-half-mile incline to where miners currently are working.


Miners dig and bag material recovered from the rock that is laced in dark shimmering graphite, which is responsible for the traces of vanadium that produce tanzanite’s violet blue coloring. Other minerals found with tanzanite include pyrite, diopside, peridot, quartz, garnet and tourmaline. Representing 40 percent of world production, TanzaniteOne had its greatest annual tanzanite production of 2.38 million carats in 2011;

Bags of rock obtained from the mine are transported to a modern ore-processing plant TanzaniteOne built on site, where the rock is run through dense media separators that separate the material down to less than 30 mm in size. The company then recycles water through the system, and donates discarded rough to the community so local residents can pick it over to retrieve stones to resell. 2.5 million carats are projected for 2012. 

In the sort house at TanzaniteOne’s mining site, rough is further separated into 12-mm, 5-mm and 3-mm stones, with rough under 3 mm discarded. The rough then passes through an automated optical sorting and primary grading scanner, which Jean Harris, sort house manager, hails as a first in the gem trade. “Designed in Germany to separate color glass,” he says, “the machine is 98 percent to 99 percent accurate in separating variations in tanzanite color.” The stones then move to hand sorters, shown at right, who further separate stones by quality into gem grade, low grade and those that will be discarded. Throughout the sorting and grading process, the stones are weighed, recorded and tracked.

The tanzanite crystals, already separated by size, are further divided by color grade: A, B, B light, intense blue, violet, burgundy. The deeper the color, the rarer the tanzanite. Larger stones are often darker, smaller ones favor pastel shades. While some natural violet blue tanzanite is recovered at current depths, the bulk of material is an earthy brown color that is heat-treated to enhance its color. This quick, low-temperature, permanent and stable enhancement produces the rich vilotet blue shades for which tanzanite is known.

In response to a July 2010 government export ban on gem rough larger than 5 carats — an effort to develop Tanzania’s domestic cutting industry — TanzaniteOne hired and trained 18 local lapidaries to cut stones. About 60 percent to 70 percent of its production is cut on site. Industrywide, the government, along with the Tanzania Mineral Dealers Association (TAMIDA), is developing lapidary training for locals in Arusha, with a focus on recruiting women.


TanzaniteOne developed its lapidary skills to mirror those of its top customers, Indian manufacturers serving the U.S. market. The Tanzanite facility uses two different cutting techniques, Integral Production Line (IPL), an Israeli technology that realizes 40 percent yield and is most often used for fancy cuts, and Imashi, a Japanese technology that offers 45 percent to 50 percent yield and produces cuts most preferred by Indian clients. Tanzanite is a trichroic gem that radiates blue, violet and burgundy from different crystal axes. “If the stone is skillfully cut, all of the colors can be seen,” explains Sarah Martin, marketing manager for The Tanzanite Experience (TTE) retail shops. She says skilled lapidaries can orient the cutting to produce a stone that appears either more blue or more purple.

Tanzanite is cut in a variety of shapes, with trillions, cushions and ovals the most popular. TanzaniteOne is exploring different cutting styles, such as faceted beads for lighter-colored commercial-grade goods, to test market through its TTE stores in Arusha and Dar es Salaam. TTE sales represent 9 percent of overall company revenues — $20.8 million in 2011 — and support Tanzanite Foundation community projects.


A nonprofit marketing and social outreach organization, the Tanzanite Foundation invests in such programs as constructing schools, a medical clinic and community center; providing supplies and lunches to area schools and pumping fresh water to the local community. The foundation also sponsors training programs for local Maasai women in wire-wrapping commercial tanzanite with the goal of selling their finished jewelry through TTE. 

Article from the Rapaport Magazine - June 2012. To subscribe click here.

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