Étude mineralogique, chimique et diffractometrique de quelques wolframites du Brésil

Ten wolframite samples from nine Brazilian mines and occurrences and one from Portugal were mineralogically and chemically studied and X-Rayed in order to determine their characteristics and the relations between them . A short description of the mineral deposits and the samples is given. Measured gravities, reflectivities and microhardnesses show continuous variations, generally however without correlation. On the contrary, chemical analysis (determination of MnO/FeO ratio or Hubnerite/Ferberite) and diffractometric measurements (angle 2o(512)) demonstrate a good linear graphical correlation within the limits of experimental precision. As a result, this graph enables one, with a fast diffractometric determination, to locate an unknow wolframite in the Hubnerite-Ferberite series. With regard to the classification of the wolframite occurrences they all appear to belong to the pneumatolytic type with transitions to hydrothermal veins of low temperature and to the pegmatitic type with the increase of temperature.