Which of the following methods is used to concentrate cassiterite ore?

Cassiterite consists of non magnetic particles stannic oxide $\left({\mathrm{SnO}}_2\right)$ and magnetic particles ferrous tungstate $\left({\mathrm{FeWO}}_4\right)$.

The beneficiation of Cassiterite (tinstone) can be carried out by gravity separation and magnetic separation. The ore is crushed to a fine powder and concentrated by gravity separation by washing with current of water when most of the lighter gangue particles are removed. And, Ores made up of magnetic and non-magnetic particles can be separated by magnetic separation. In this method, magnetic particles get attracted towards a magnet leaving a non-magnetic part.