I. SELECTIVE FLOTATION
Twin Metals has been working since early 2012 on a comprehensive metallurgical testwork program aimed at defining a commercially viable process flowsheet that will recover copper, nickel, gold, platinum, and palladium to payable products. This metallurgical testwork program included mineralogical assessments, laboratory bench scale testing, and pilot scale testing.
A variety of samples have been tested as part of the metallurgical test program. In particular to the flotation flowsheet development and pilot plant programs undertaken in 2012 and 2013, the majority of samples were obtained from a large PQ drilling campaign which acquired almost 70 tons of mineralized material.
Two flotation flowsheets were investigated. The two flowsheet circuits considered primary grinding and multi-stage flotation including rougher, regrinding of the rougher concentrate and two or three stages of sequential cleaning.
The first flowsheet involved production of a bulk concentrate that would require onsite processing rather than direct sale to smelters. Results of the bulk flotation showed very high copper recoveries and solid nickel recoveries. Concentrate grades and recoveries can be found in the summary reports available on our website.
The second flowsheet (selective flotation) involved production of a marketable copper concentrate and a marketable nickel concentrate. The sequential flotation tests indicated very little loss of copper recovery and minimal nickel recovery losses in comparison to the production of a bulk concentrate. Testwork indicated that nickel deportment to the copper concentrate was minimal. Copper concentrates of almost 25% copper with less than 1% nickel, and nickel concentrates of approximately 10% nickel with less than 5% copper were achieved. Ongoing testwork is focused on upgrading the nickel content of the nickel concentrate. Specific values and trends are represented in the summary reports available on our website. Note that these results were achieved during bench and pilot plant programs using the composite ore samples as described above; additional testwork programs are planned to investigate variability in ore response to the flotation flowsheet as a mine plan is developed for the deposit.