Observation

The expected answers were:

(a) (i) Gravity concentration may be defined as the separation or concentration of two or more minerals of different specific gravities. This method favours separation of mineral that are not very close in terms of densities e.g. separation of iron ore from silica impurities using shaking table, sluice box, jig, multiple separator, Humphrey spiral etc

(b) (i) Crushing: Crushing is done directly to reduce run of solite ore to particles sizes suitable for grinding. The process may be achieved through primary, secondary and tertiary stages. In each of these stages, machines are used in reducing ore from larger to smaller sizes with screens in between as determining apertures. These machines include jaw crusher, gyratory crusher, cone crusher, impact crusher etc.

     (ii) Grinding: Products of crushing process are accepted as feeds and produced to particle sizes suitable for concentration as finished products. Grinding is achieved by the use of tumbling mills employing different media such as steel rods, steel balls, pebbles or autogeneous. The name of the medium usually defines the mill e.g. ball mill, rod mill, pebble mill or autogeneous mill.