[en] Co-ordinated mineralogical techniques, supported by partial bulk-rock chemical analysis, have been applied in an investigation of drill-core samples of granite from both unaltered and sericitized zones in the Urgeirica uranium deposit, Viseu-Guarda region, Portugal. Significant proportions of the whole-rock uranium values are accounted for by uraninite, although titanium-uranium phases, formed from lateration of ilmenite, are important in the sericitized rocks. The distribution of uranium in the latter suggests several stages of development during alteration. Comparisons are made between the mineralogical and chemical characteristics of uraninite in these samples and vein-uraninite (pitchblende). The results are discussed in relation to the genesis of the vein-type mineralization. (author)