gems, garnet, grossular, hessonite, India, Orissa, tourmaline, sillimanite

The state of Orissa in eastern India has emerged as an increasingly important source of gemstones. Since 1989, rising quantities of rhodolite garnets from the region have been seen, followed by notable finds of aquamarine and ruby. At the 1993 Tucson Show, Amar J. Jain presented a 2.99 ct faceted alexandrite and dark grayish blue tourmalines from Orissa, one of which—a 1.74 ct emerald-cut specimen—showed gemological properties consistent with tourmaline from other locations, including refractive indices of 1.620 and 1.640, birefringence of 0.020, and specific gravity of 3.11. Hessonite (grossular) garnet is also being mined near Kanta Bhaji in the Kalahandi area, with faceted stones ranging from reddish orange to orangish brown; many exhibit a pronounced “roiled” appearance typical of Sri Lankan hessonites, sometimes resembling translucent sard. A 2.19 ct orange stone tested with an R.I. of 1.748 and S.G. of 3.65, confirming it as hessonite. Following the show, the editors received a report from Shyamala Fernandes of the Gem Testing Laboratory in Jaipur describing a December 1992 find of chatoyant sillimanite, initially misidentified and marketed as “moonstone cat’s-eye.” Identified as sillimanite, the material exhibited an R.I. of 1.659–1.678 (1.66 spot), S.G. of 3.25, biaxial optic character, and Mohs hardness of 7–8. Microscopy revealed parallel acicular inclusions responsible for the chatoyancy, along with “fingerprint” two- and three-phase inclusions and black platelets. The sillimanite occurs in colors ranging from colorless to gray, pinkish brown, yellow, green, and blue-green, typically in lighter tones, and most cabochons—some up to 20 ct—display sharp cat’s-eyes and a vitreous luster. Though precise production data is lacking, the material has been readily available in Indian markets since its discovery.