Gem Focus June 2022: Tsavorite; the fresh green variety of garnet family..

Posted on June 15, 2022 by Çiğdem Lüle, PhD, FGA, GIA GG, DGA

The second half of the 20th century witnessed two very important gem discoveries in East Africa. Renowned geologist, the late Campbell Bridges notes that he first encountered a green variety of grossular garnet in Zimbabwe in 1961. It was his second encounter with the green garnets, however, that garnered attention from the high-end jewelry brands. Starting in Northern Tanzania in 1967, Campbell would follow a series of geologic clues that would eventually lead him across the border into Kenya and the primary deposit of richly colored, vivid green garnet. By the 1970s, Mr. Bridges moved to Kenya, found more tsavorite sources in the southeast and started a steady mining operation. Tiffany & Co. was very interested in this new green gemstone and made a point of giving it the name tsavorite, in homage Tsavo National Park area in Kenya, a source of this stone. Thanks to Mr. Bridge’s determination and dedication, another beautiful garnet variety has joined the realm of fine gemstones. Tsavorite garnet, yellow sapphire, and gold brooch by Tiffany & Co. Courtesy of Heritage Auctions. Grossular, a species within calcium-aluminum group garnets, has several gem varieties mostly known as hessonite (brown, yellow through red), hydrogrossular (pink and green massive variety) and tsavorite (green through yellowish green). Identification of tsavorite is fairly straightforward due to its under the limit refractive index of 1.74 and single refraction. The color is due to vanadium but it doesn’t have a characteristic visible spectrum. Neither synthetic production, nor treatments are known for tsavorite in the marketplace, although one must always be aware of clarity enhancement for any gemstone with a surface reaching fracture. Faceted tsavorite garnet, 65.72 ct, measuring 23.42 x 20.20 x 16.53 mm. Block D, Merelani Hills, Lelatema Mts, Simanjiro District, Manyara Region, Tanzania. Sold for $325,000.00 in 2015. Courtesy of Heritage Auctions. The common knowledge is that red garnets are abundant, yet it is not easy to come across a fine quality rhodolite or spessartine larger than 10 ct sizes. Similarly, in the orange category, fine-grade mandarin garnets are achieving great popularity and higher per carat prices compared to a decade ago. Saturated yellow hessonites are always sought after. Rarer green garnets such as demantoid and tsavorite remain in demand. Popularity of tsavorite garnet has increased recently as the gem’s most famous source is in full production. Unfairly marketed as an “alternative” to emerald in the past, tsavorite earned its niche in the market due to limited availability and greater public awareness. Today, demand in the tsavorite market is consistent with expectations. Tsavorite garnet possesses key attributes that support a further increase in market share. These include the purity and intensity of color, the relative lack of treatments used in the garnet group, and a color that is increasingly popular in recent years. Tsavorite is often featured by designers of high-end jewelry. In its fine and extra fine grades, tsavorite is expected to display a rich green color that may be accompanied by a very slight blue secondary color with high transparency. The examples with lighter tone and lower saturation are marketed as “mint garnets” and are as popular due to their lower price points. Recent production increased the number of larger and better stones in the market. High-end buyers are given more options while understanding that the beauty and rarity of tsavorite clearly justify its price.   Photo in Header:  Tsavorite garnet, diamond and white gold bracelet. Courtesy of Heritage Auctions. Author: Çiğdem Lüle, PhD, FGA, GIA GG, DGA

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