Comminution effects on mineral grade distribution

Every mining operations is followed by a beneficiation process aimed to deliver quality material to the transformation industry. Mainly, in mineral processing comminution and grinding of extracted ore, are crucial operations for the following separation steps in order to obtain valuable minerals from gangue.

Comminution is the most energy consuming phase and the quality of the results is strictly related to the characteristic of the material under treatment.

A preliminary study has been performed in order to understand the crushing behaviour of a mixed sulphide ore, containing galena and sphalerite, and the distribution of the two target minerals among the different sized products of the process.

Ore samples have been examined and characterized by means of thin sections observation and SEM analyses for the determination of the free grain size, while XRD quantitative analyses have been performed for the definition of the grades.

The selected crushing circuit comprises lab-scale impact crusher, jaw crusher, disk mill and rod mill. For each stage of the process products below the free grain size threshold have been collected and particle size analyses have been carried out.

Comminution products were divided in dimensional classes suitable for flotation separation, ranging between 0.250 and 0.075mm and XRD analyses showed a variable mineral grade distribution varying with the reduction in dimension of the products.

This important trend should be considered for further investigation related to an efficient froth flotation separation.