corundum, geology.11, sources.12, Rwanda.12, gems

Yet another new locality for natural blue and treatable sapphire surfaces in this description of material from the Cyangugu district of South West Rwanda. Following summary descriptions of the sapphires' geologic setting and apparent origin from alkali basalts, the results of testing 20 samples is reported. Absorption spectra (visible and infrared), quantitative chemistry (microprobe), and microthermometry were performed on two specially prepared samples. Ten prepared specimens were examined by SEMEDS for inclusions, and eight rough samples were also studied by SEM for detailed surface analysis. The appar ently meticulous methodology yielded high-quality detailed information that is a welcome addition to the gemological literature, despite the small sample size. Numerous illustrations also indicate that this material yields fine-quality gems of brilliant blue color. However, no mention is made of its commercial availability or potential supply.