Lara Exploration Ltd.: Lara Exploration Announces Positive Preliminary Metallurgical Test Work for the Planalto Project in Brazil
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The test work conducted by Blue Coast included studies on chalcopyrite liberation, rougher and cleaner flotation and comminution, QEMSCAN mineralogy studies and some trialing of gravity concentration on the final copper concentrate to see if a commercial grade gold-copper concentrate could be attained.
Mineralogical analysis showed chalcopyrite liberation to be 71-73 % at 80% passing 75 microns, whereas with the coarser grind of 106 microns, the liberation was only 55%. A portion of the chalcopyrite has been shown to occur as fine-grained disseminations enclosed in silicate minerals and as such not readily liberated. A total of eight flotation tests were trialed, using different primary grind sizes and different frothing and collector agents to determine the best flow sheet to achieve an optimum copper grade and recoveries into the rougher concentrate. Copper flotation recoveries into the initial cleaner concentrates were found to be low (as low as only 13% Cu), so further testing at the cleaner stage incorporated a regrind step on the rougher concentrate to attain a cleaner flotation concentrate at a commercial copper grade.