1984-11-07_REVISION - M1983052 - Laserfiche WebLink

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i The cyanide tests are run at a pH of 11. 5 (lime adjusted) in 6 . 5 ft3 cement mixers . A solution to ore ratio ranging from 1:1 to 3 :1 is utilized. At the end of each test, the solutions are alkaline chlorinated with calcium hypochlorite (swimming pool bleach) at a pH of 11 . 0+. The cyanide is fully oxidized by using a 4 : 1 oxidizer to CN- ratio. In order to eliminate the last vestiges of cyanide, complexed or otherwise, the solution pH is reduced to 7 . 0 prior to releasing the samples from the laboratory. Marathon ' s pilot plant is an experimental gravity concentration facility used to process 100 ton samples of crude ore to obtain a heavy mineral , gold bearing concentrate. No hazardous chemicals or additives are used in the plant . Bulk samples are taken in the field, screened and concentrated in the pilot plant, and sent to the laboratory for treatment to obtain analytical data. Twice a month or so, 750 pounds of concentrates produced in the pilot plant are cyanided in the laboratory to obtain assay verification of the gold content. This treatment results in the actual production of small amounts of gold. The techniques used to handle and treat these large samples are essentially the same as described above for the smaller samples. The only significant difference is that cyanide solutions are not disposed of but rather are stored in the laboratory as either pregnant or barren solution for gold recovery or reuse in additional concentrate analysis and testing. When necessary to bleed small amounts of barren solution, the solution is pumped to the alkaline chlorination system for treatment and neutralizing prior to release. No toxic material is disposed of in any manner. Cyanided ore pulps, when through with the alkaline chlorination pH adjustment procedure , have a pH of 7 . 0 and contain only minor amounts of 3