Possibilities and Limitations of Gravity Concentration as Applied to Pitchblende Ores at Port Radium, N. W. T.

"IntroductionExperience at Eldorado has been gained with a variety of mill feeds. That is, the actual mode of occurrence of the pitchblende varies to such an extent that gravity concentration has at times been decidedly unattractive and at others highly successful. Because of this, the type of ore necessary for economic recovery of pitchblende have become well known. Also, those types which do not lend themselves to gravity concentration have become familiar. In general, it may be said that when the pitchblende occurs free, to a large extent, from sulphides or arsenides of high specific gravity, and when the bulk of the pitchblende is localized rather than disseminated, excellent recoveries, high ratios of concentration, and good grades of concentrates , will result from proper gravity concentration. On the other hand, if the ore contains pitchblende intimately or otherwise mixed with large quantities of arsenides or sulphides, or if the pitchblende is finely disseminated, gravity concentration alone will yield high recoveries only at the expense of very low-grade concentrates and low ratios of concentration.According to Taggart, the ease with which gravity separation may be effected is determined by the value of the following ratio: []It is stated that when the ratio is above 1.75, gravity separation can be expected to be easy. Thus with pure U308 (S.G. over 9) and gangue consisting chiefly of siliceous material, the process can he expected to be entirely successful even when carried on at very fine sizes. Unfortunately, the term pitchblende covers a great diversity of material. Although some of the mineral occurs pure enough to have a specific gravity of about 7, the average is much lower than this and is probably well under 5. Some of the pitchblende particles have a specific gravity so low that gravity concentration fails completely. It may also be said that no degree of grinding will produce free pitchblende of sufficient density from such particles. This, then, represents the most important limitation to the application of gravity separation to pitchblende ores."