Because of the presence of skillful operators, the severe requirements to the raw materials and the hightechnical level of the flotation process, the "Kyoei Chemical Industries" are producing a high grade fluorite concentrate (CaF₂>98%). Unfortunately, these performances will worsen inevitably as the properties of the materials change perpetually and skillful analysts go missing every year. To identify the raw material's properties and grasp the optimum conditions for an efficient separation, a so-called timeless "checking" system has been established and tested on an operating grinding-classifying-flotation circuit. The system comprises four (4) operations: designation of the sampling points, preparation of samples, x-ray powder diffraction analysis and microscopic counting of particles. The results of the testing has revealed a great presence of gangue particles in the -420+149 im fraction of the Akins classifier and suggested reducing to 297 pm the cut off point of the classifying circuit.

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Flotation methods of Tizapa ore, which is pyrite rich complex sulfide ore and occurs in the center of Mexico, have been investigated in order to concentrate silver and zinc. In the lead flotation for concentrating silver, the following three methods were tested: (1) the rougher flotation using ethyl aerofloat as a collector and Na₂SO₃ as a depressant for sphalerite and pyrite, followed by a 5 stage cleaning, (2) the same rougher flotation, and a single stage cleaning at an elevated temperature (60°C), and (3) the single stage hot flotation (60°C) without depressant. In all methods, lead concentrates were obtained with about 70% silver recovery. And then, zinc flotation tests were carried out using lead flotation tailings obtained by the above methods. In the zinc flotation, potassium dichromate was found to be the effective depressant for pyrite. The method (1) gave a poor zinc recovery. On the other hand, in the methods (2) and (3), zinc concentrates containing as high as 51% zinc were obtained with 56% and 69% zinc recovery, respectively.

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