Show LESS FINELY CRUSHED MINERAL GRAINS NOW YIELD TO FLOTATION it has generally been held that for the treatment of ores by the flotation process crushing to minus 65 mesh is required this was the size limit of grains which experience seemed to indicate when oils chiefly were used experimental peri mental work at the moscow field office of the united states bureau of mines shows that sands crushed to not nearly this degree 6 of fineness can be readily floated in some of the work at that station as coarse as 20 mesh sands are amenable to flotation even coarse sands that expose at their surfaces very small specks of the flo table material may be lifted this broadening of the field of flotation is due to the development in recent years of the promoter class of reagents aen agents ts these substances so greatly increase the vigor of a mineral that correspondingly larger grains may he lifted flotation is rapidly expanding into the size range of table concentration and the cost of crushing for flotation is gradually being reduced |