Quartz could be activated by metal ions dissolved from wolframite surfaces, making it difficult to separate wolframite from quartz. In this study, sodium silicate used as depressant was investigated in the flotation of fine wolframite. Sodium silicate showed the selective depression on the activated quartz, and the flotation separation of fine wolframite could be achieved by depressing quartz. It was revealed that the adsorption of sodium silicate on activated quartz surfaces was more obvious than that on wolframite. Si(OH)(4) and species of aqueous sodium silicate preferentially reacted with activated quartz surfaces and prevented the octyl hydroxamic acid adsorption, further decreasing its floatability.