Tin and tungsten minerals are dense, but density separation becomes less forgiving as particles become finer. Several process errors can combine to create losses that are blamed on the final separator.
Valuable minerals are made finer than necessary
Cassiterite and some tungsten minerals can report to fine fractions after repeated crushing, aggressive scrubbing or unnecessary regrinding. Recover liberated coarse particles early and regrind selected middlings rather than the whole stream.
Broad size ranges compete in one separator
Coarse and fine particles have different settling behavior. A machine adjusted for one range may produce poor selectivity in another. Classification is not optional preparation; it is part of gravity separation.
Slimes change slurry behavior
Ultrafine clay and mineral particles can increase viscosity, disturb stratification and carry valuable fines into tailings. Desliming decisions should be based on assays of the fine fraction because rejecting slime can also reject valuable mineral.
Water and feed are unstable
Tables, spirals and other gravity devices depend on controlled flow and solids loading. Hand feeding, surging pumps and changing dilution make the separation zone move continuously.
Measure losses by size
A bulk tailings assay confirms that value is being lost but does not explain why. Screen or classify tailings into practical size fractions and test each fraction. The result shows whether the next action is better classification, liberation, feed control or a specialized fine-recovery stage.