Sulphide ores of metals are usually concentrated by froth flotation...

Argentitie or Silver glance, $\mathrm{Ag}_2 \mathrm{~S}$ is an ore of silver. Silver is extracted from argentite by the mac-Arthur and Forest process (leaching process). $$\begin{aligned} & \mathrm{Ag}_2 \mathrm{~S}+4 \mathrm{NaCN} \rightarrow 2 \mathrm{Na}\left[\mathrm{Ag}(\mathrm{CN})_2\right]+\mathrm{Na}_2 \mathrm{~S} \\ & 4 \mathrm{Au}+8 \mathrm{KCN}+2 \mathrm{H}_2 \mathrm{O}+\mathrm{O}_2 \rightarrow 4 \mathrm{~K}\left[\mathrm{Au}(\mathrm{CN})_2\right]+4 \mathrm{KOH} \end{aligned}$$ Related Theory Leaching is the selective dissolution of the desired mineral leaving behind the impurities in a suitable dissolving agent.