Serendibite from Sri Lanka

from secondary deposits in the Ratnapura area in the second half of the 1990s increases the number of gems containing essential boron from this island (tourmaline, dumortierite, boron-rich kornerupine [or prismatine, according to recent mineralogical studies], and sinhalite). To date, serendibite has been reported from 11 localities: Sri Lanka (type locality near Kandy), United States (three occurrences), Russia (two occurrences), Ukraine, Tanzania, Canada, and Madagascar (two localities). At all of these localities, serendibite occurs in metasomatic high-temperature calc-silicate rocks (skarns), mostly of granulite facies (Grew et al., 1990, 1991a,b; Grew, 1996). The occurrence of gemquality serendibite crystals in secondary deposits near Ratnapura, Sri Lanka, is consistent with the derivation of these gem gravels from granulite-facies metamorphic rocks. According to modern mineralogical examination (see, e.g., Kunzman, 1999), serendibite is a triclinic Ca-Mg-Al-B-silicate which can also contain distinct amounts of Fe2+ and Fe3+. Since 1997, gemologist and gem dealer D. Palitha Gunasekera of Ratnapura has reported encountering three gem-quality samples of serendibite, weighing 0.35, 0.55, and 0.56 ct as faceted stones( pers. comm., 1997–2001). A merchant in Kolonne showed him the first (smallest) sample as a 1.25 ct pebble. This rough sample was said to originate from Ginigalgoda, near Kolonne in the Ratnapura district. Mr. Gunasekera submitted the 0.35 ct stone faceted from this piece of rough (figure 1) to the GIA Gem Trade Laboratory for identification in autumn of 1996 (Reinitz and Johnson, 1997). It was subsequently purchased by one of the present authors (EG) and identified independently as serendibite by KS in 1997, also using X-ray powder diffraction. A review By Karl Schmetzer, George Bosshart, Heinz-Jurgen Bernhardt, Edward J. Gubelin, and Christopher P. Smith