As previously noted, numerous tests were made in the pilot plant, under a variety of conditions, to determine the best flowsheet for recovering mica. Based on the results of the tests, the flowsheet shown in figure 1 ultimately proved best for the acid cationic method.

The ore was ground in a rodmill in the presence of sodium hydroxide to aid in dispersing and removing clay slimes. The rodmill was equipped with a 20-mesh trommel, and grinding was adjusted to the point where the trommel oversize consisted of high-quality mica.

The trommel undersize was deslimed by two-stage desliming in a hydroseparator and a bowl-rake classifier to remove the minus 200-mesh fines. The ore, after grinding and desliming, contained about 1 percent minus 200-mesh material. The pulp then passed to a conditioner, where the reagent for pH control and quartz depression was added. The pulp from the conditioner flowed by gravity to a bank of rougher flotation cells, where the amine collector was added to the first cell. A rougher flotation concentrate was recovered and cleaned three times to produce a finished mica concentrate. The middlings were recirculated countercurrent to the pulp flow in the cleaner circuit and. ultimately joined new feed at the head of the roughing circuit. The mica flotation concentrate and the 20-mesh trommel oversize, when combined, accounted for a recovery of about 77.5 percent of the mica present in the feed in a product containing 98.1 percent mica. The results of the continuous test are presented in tables 4 and 5.