Faceted Demantoid Garnet with Spectacular “Horsetail” Inclusions
The Laboratoire Français de Gemmologie (LFG) received for analysis an example of the yellowish green variety of andradite garnet known as demantoid. The gem was cut in such a way that spectacular “horsetail” inclusions are anchored at the center of the table (figure 1). These inclusions are actually fibers (figure 2), which are present in some demantoids from the Ural Mountains (Russia) but also from Val Malenco (Italy), Baluchistan (Pakistan), as well as from Kerman (Iran) (W.R. Phillips and A.S. Talantsev, “Russian demantoid, czar of the garnet family,” Summer 1996 G&G, pp. 100–111; Spring 2007 Gem News International, pp. 65–67; I. Adamo et al., “Demantoid from Val Malenco, Italy: Review and update,” Winter 2009 G&G, pp. 280–287; I. Adamo et al., “Demantoid from Balochistan, Pakistan: Gemmological and mineralogical characterization,” Journal of Gemmology, Vol. 34, No. 5, 2015, pp. 428–433).
The exact origin and composition of the “horsetail” inclusions in demantoids are still under discussion. Those in demantoids from Russia, Italy, and Pakistan were reported to be chrysotile, and those from Iran calcite. On the other hand, a recent study of these inclusions in some demantoid garnets from the Ural Mountains showed that these might be hollow channels, sometimes containing minerals from the serpentine group, possibly the result of superficial weathering (A.Y. Kissin et al., “‘Horsetail’ inclusions in the Ural demantoids: Growth formations,” Minerals, Vol. 11, No. 8, 2021, article no. 825). Thus, the exact mechanism of formation of the “horsetail” inclusions in demantoid garnets is again open for discussion.
