Gems & Gemology, Summer 2002, Volume 38, No. 1
New Chromium- and Vanadium-Bearing Garnets from Tranoroa, Madagascar
Karl Schmetzer, Thomas Hainschwang, 和 Heinz-Jürgen Bernhardt, and Lore Kiefert
Pyrope-spessartine garnets from Tranoroa, in southern Madagascar, contain appreciable Cr and somewhat lower V contents. Although these elements are responsible for the color-change behavior of similar garnets from the nearby Bekily area, the Tranoroa samples show only a slight change in color appearance from day or fluorescent light (brownish purple-red) to incandescent light (purplish red). Characteristic internal features in the Tranoroa garnets include networks of rutile needles and strain patterns caused by anomalous double refraction. Additional inclusions are graphite, quartz, negative crystals, apatite, zircon, and monazite. One Cr-bearing spessartine from the same area is also described.