Abstract: The density of the material in the jig bed is measured in consecutive short segments over the jig cycle, the time period of each segment being not greater than one-tenth the cycle time of the jig, to determine the density signature or profile of the jig. By controlling the operating parameters (e.g. inlet and outlet valve opening and closing, underbed flow rate, discharge gate position and jig working air pressure) of the jig, the density signature or profile is maintained within a control envelope for efficient stratification of the mineral.

Abstract: Crushed particles of coal, ores or industrial minerals or rocks are comminuted by feeding them through a feeder (14) into a cyclic stream (19, 22, 38, 39, 41) of cryogenic process fluid such as liquid carbon dioxide and conducting the process stream with the entrained mineral particles to a comminuter (17) and through a zone therein of mechanically generated high frequency vibratory energy, preferably ultrasonic. The comminuter (17) may be multistage with means for re-cycling oversize mineral particles and, after leaving the comminuter (17) the process stream (38) is conveyed to a separator (18) for extracting the comminuted particles and re-cycling the cryogenic fluid to the feeder (14). The low temperature of the process stream is maintained by refrigerating means (16) and losses of the fluid are made up by supplementary fluid fed to the stream.

Abstract: A method of radiation measurements on slurries where the slurry is pumped to a pressure where the volume of gases in the form of gas-bubbles is reduced below a level where the gases effect the radiation counts. The slurry pressure is raised to a pressure in the range of 100 p.s.i. to 500 p.s.i. (690 kPa to 3.5 Mpa) absolute using a positive displacement pump.