Gem News International Gems & Gemology, Spring 2015, Vol. 51, No. 1

Fine Tsavorite and Spinel

Green tsavorite
Figure 1. This spectacular 12.46 ct tsavorite recently returned to Bruce Bridges’s inventory after being in a collector’s possession for many years. Photo by Robert Weldon/GIA; courtesy of Bridges Tsavorite.
Bruce Bridges (Bridges Tsavorite, Tucson) said that fine stones often return to his inventory after years in a collector’s possession. At the AGTA show, he showcased a vivid, top-quality 12.46 ct cushion-cut tsavorite fashioned some 15 years earlier, which made its way back into the market in the last two years (figure 1). As tsavorite rough has a high value, gems are typically cut to maximize weight. Rough is typically recovered as long, thin asymmetrical fragments that lend themselves to pear, marquise, and trilliant shapes. This example’s unusual square cushion shape, large size, color, and clarity make it a notable and rare gemstone.

Tanzanian red spinel
Figure 2. This 18.21 ct Tanzanian red spinel was fashioned from material recovered from one of four enormous multi-kilogram crystals reputedly found in the Ipanko ruby and spinel mining area near Mahenge, Tanzania. Photo by Robert Weldon/GIA; courtesy of Bridges Tsavorite.
After seeing the wealth and variety of gems on display at the Tucson gem shows, it might be easy to come away with the impression that fine colored stones are not particularly rare. Yet the truly magnificent stones are extremely rare and often have a memorable provenance. One such gem is the 18.21 ct triangular cut red spinel Bruce Bridges showed us at his AGTA booth (figure 2). According to Bridges, this magnificent gem was cut in 2007 in Bangkok from rough recovered in one astounding find in Tanzania’s Ipanko mining area that yielded several giant spinel crystals, one of which weighed in at over 50 kg. A number of other dealers at this year’s show, including Axel Henn, also displayed fine gems from this one extraordinary discovery.

Donna Beaton is colored stones technical advisor for content strategy at GIA.