About us

Gemos Gems . From the time it was established in 1991, Gemos Gems has purchased rough colored stones from East Africa. In the early 1990s, the company bought rough ruby and tanzanite in Nairobi. By the mid-1990s, Gemos Gems found that Arusha, Tanzania, was a better place to source tanzanite and began purchasing from dealers who bought the stones from Maasai tribesman.

Today Gemos Gems is one of the ten sightholders listed by TanzaniteOne, which operates in a manner similar to the De Beers supplier of choice system. For Gemos Gems, the fixed-price rough lots from TanzaniteOne are well graded, sorted, and organized, making it easy to calculate costs and profit margins. The company also buys an equivalent amount of rough on the open market from other miners and dealers in Tanzania. The rough supplied by Arusha’s independent dealers has become very well graded, as opposed to the mixed lots and mine runs they supplied several years ago.

Gemos Gems has seen wide fluctuations in supply and prices. Today’s prices are stabilized, as the miners and dealers control the material offered for sale to better meet the demand.  the company’s best period in the tanzanite business was around 2012 through 2013, when Chinese demand exploded but then cooled. Now their main market is once again the United States. Gemos Gems sells to wholesalers and jewelry manufacturers, but perhaps their most important customers today are television shopping networks and the manufacturers that make their jewelry.

Gemos Gems feels that tanzanite is now a mainstream colored stone like the “Big Three,” and although supply has fluctuated it can still meet large-scale demand. Eighty percent of the company’s business is now in tanzanite, with other Tanzanian stones like spinel, rhodolite, spessartine, and tsavorite making up the remaining 20%.

Gemos Gems factory in Jaipur

Gemos Gems has a traditional Jaipur factory where preformers prefer to work sitting on the floor. Each preformer averages 400 stones a day. Photo by Andrew Lucas, courtesy of Gemos Gems

At the factory, we followed the entire process from rough grading and preforming to calibration and faceting. Each stone could be completed in about two hours. The smallest size of rough Gemos Gems manufactures (approximately 0.1 gram) had about 6% weight retention, while the larger sizes (1 gram) retained about 25%. Most were cut as rounds and ovals, with other shapes cut to order. As with Gemos Gems, their calibration tolerance is 0.2 mm.

At the factory, we followed the entire process from rough grading and preforming to calibration and faceting. Each stone could be completed in about two hours. The smallest size of rough Gemos Gems manufactures (approximately 0.1 gram) had about 6% weight retention, while the larger sizes (1 gram) retained about 25%. Most were cut as rounds and ovals, with other shapes cut to order. As with Gemos Gems, their calibration tolerance is 0.2 mm.

The company buys rough from dealers in Tanzania and in the domestic Jaipur market. The supply of tanzanite has fluctuated over the years, but the focus on smaller sizes in manufacturing is due to the Tanzanian restrictions (figure 15).

Rough sorting of tanzanite at Gemos Gems

Figure 15. While the facet-grade tanzanites available to Gemos Gems  are under one gram in size, the company still has an extensive rough sorting system for shape, color, and clarity that provides consistent quality ranges for cut stones. Photo by Andrew Lucas, courtesy of Gemos Gems 

For most tanzanite rough, Gemos Gems  follows a heat treatment process similar to that of AG Gems, heating the rough after preforming (though we did see some lighter-color rough being heated before preforming). No time is wasted preforming material that might not have sufficient color quality for faceting, even though this leads to a higher percentage of stones that burst from preexisting fractures in the rough.

Gemos Gems classifies its tanzanite qualities according to standard terminology for the global trade. Colors are separated by tone and saturation into A, A+, AA, AA+, AAA, and the finest grade of AAA+. For stones with the same size, the spread in price from A to AAA+ can be as much as 300%. The grades are set according to Gemos Gems ’s master stones, which are chosen to match the grading of global customers. Many of these customers are wholesalers, manufacturers, and jewelry television networks. 

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