CONCENTRATION AND DETERMINATION OF GRADE IN TESTS ON SILLIMANITE IN IDAHO SCHIST*

A bstract Laboratory batch tests have demonstrated that the Idaho sillimanite schist was amenable to beneficiation by common ore‐dressing methods. The minable schist, containing an average of about 7.8%, sillimanite, was crushed to pass 35 mesh and concentrated by a combination of tabling and flotation. Grade was determined by petrographic examination of fractions obtained by heavy‐liquid separations in a centrifuge. This method was used as a positive means of separating the sillimanite from the gangue minerals. Photomicrographs illustrate the character and quantity of sillimanite in the various concentration products.