Historical observations on oxygen-bearing compounds of platinum and palladium in Minas Gerais, Brazil

Abstract

Dark brown to black compounds associated with native gold were discovered three hundred years ago in Minas Gerais, Brazil, and have been known since then as ouro preto (black gold). These compounds were correctly determined as oxygen-bearing compounds of platinum - palladium - iron as early as 1833 and 1837, but the oversight of the presence of major iron in their composition led to an erroneous definition of palladinite and to the much-delayed recognition of a group of platinum-group-element oxides.