This report has two parts to it discussing mineralogical examination of pitchblende concentrates and nitric acid digest residues. Part I gives the results of a cursory examination with the petrographic microscope of samples of pitchblende concentrates and residues to see if there is a relationship between the mineral composition of the samples and the filterability of the residue. Part II gives a revaluation of the data in Report BMI-241 on the mineral composition of two residues from the nitric acid digestion of pitchblende concentrates at the Rallinckrodt Chemical Works.