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Wolframite impurity is removed from tin stone (cassiterite) by
Agravity (hydraulic) washing
Bmagnetic separation
Ccalcination
Dfroth flotation
Answer & Solution
Correct answer: B. magnetic separation
1. Cassiterite ($SnO_2$) is non-magnetic while the wolframite impurity is magnetic.
2. Passing the crushed ore over an electromagnetic separator pulls the magnetic wolframite aside, leaving the tin stone.
3. This is **magnetic separation**, applicable whenever ore and impurity differ in magnetic behaviour.
_Source: Samacheer Kalvi Class 12 Chemistry Vol.1, Unit 1 'Metallurgy', §1.2.4 / Evaluation Q.8_
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