Correct Answer - d
The method of levigation or hydraulic washing is based on the difference in specifigravites (or densities )of the ore and a grangue particles it is also no as gravity sepration method .
In one of the adaptations , the powdered ore is washed with an upward stream of running water when the lighter gangue particles are washed away while the hahiar ore particles (cuncentrate from) are left behind .
