... Colombian and Nigerian samples the Raman shift was around 1068-1070 cm-1 and in samples from Austria, Brazil, China, Madagascar, Russia, South Africa, Zambia, the Raman shift was around 1069-1072 ... Russia (Ural), Madagascar (Mananjary), South Africa (Transvaal), Zambia (Kafubu), Nigeria (Gwantu), China (Malipo) and synthetic ones from Tairus, Biron (hydrothermally-grown), Gilson, Chatham, ... study, the features of both Raman and IR bands (band position and band width) were clearly related to the concentration of Si in the samples. The band width was shown to be broader in the samples...