Gravity/hydraulic separation: Based on density difference between ore and gangue. Powdered ore washed over inclined vibrating table — lighter gangue washed away, heavier ore settles. Best for: oxide ores like cassiterite (SnO2), haematite (Fe2O3), chromite (FeCr2O4). Magnetic separation: Uses electromagnetic roller. If ore is magnetic (chromite, magnetite Fe3O4) or gangue is magnetic (wolframite FeWO4 impurity in cassiterite SnO2). Magnetic material deflected into separate pile. Key distinction: for tin ore purification, wolframite (magnetic impurity) is removed magnetically, leaving non-magnetic cassiterite.