gems, Brazil, topaz, imperial topaz, Capão, Minas Gerais

Mr Olsen’s paper (1971) on the origin of the topaz deposits near Ouro Preto, Minas Gerais, Brazil, shows how far we still are from understanding such a problem. Despite the author’s attempts to fit ore genesis into the regional geological evolution, the sequence of events he suggests is not in accordance with what is known from previous works (Barbosa 1961, 1969; Brajnikov 1949; Eichler 1968; Fleischer 1971). No arguments are presented either to support his hypothesis or to explain the discrepancies between previous works and his own conclusions. For reference to paper by D.R. Olsen, see this Bibliography Vol. 35, No. 8, 02 E71-23580