Abstract: The relationship of crystal structure, physico-chemical properties and floatability of MgO-containing silicate gangue minerals in copper-nickel sulfide ores was analyzed, possible ways of magnesium silicate mixed into flotation concentrate in copper-nickel sulfide ores flotation and corresponding countermeasures were summarized, the activating mechanism of metal ions on magnesium silicate and deactivating methods were emphatically researched.Finally an effective method was obtained.In this method, an efficient metal ions complexing agent is used to clean the surfaces of minerals, which will recover their original floatability.In the meantime, a selective depressant is applied to depress magnesium-containing gangue minerals.This may be the effective approach for depressing magnesium-containing silicate minerals in copper-nickel sulfide ore floatation.

Key words: Copper-nickel sulfide ores, Magnesium silicate, Metal ions, Depressant