Phase quantification in iron ore

Abstract

Quantitative phase analysis in iron ore is necessary to get a controlled blend to produce sinter feed of high quality. Optical microscopy (OM) is the routinely performed technique, but it is time consuming and affected by operator bias. In this work, Mössbauer spectroscopy, X-ray diffraction with Rietveld full profile fitting and thermogravimetric analysis were applied to investigate the reliability of a proposed OM phase quantification procedure. The method is performed on digital micrographs, with visual phase estimation of several subdivisions of the image. In this work, the authors discuss the peculiarities of the Alegria iron ore (Alegria Mine, Quadrilátero Ferrífero, Brazil), which consists mostly of haematite/goethite, with subordinate magnetite content and quartz as principal gangue mineral. The relevance of the quartz fractionation to finer grain sizes is also discussed. Results indicate overestimation of goethite in certain grain size fractions that have to be taken into account for correct phase evaluation.