The next piece of information that is of value to the operator is to know the hardness of the ore. The WORK INDEX, as the hardness is referred to, is calculated on the amount of electrical energy that is required to grind the ore to a predetermined size. Said in another way, it is the amount of work required to grind a specific size of rock down to a certain degree of fineness. Once this has been determined the amount that the ore will have to be ground must be evaluated. If you examine mineral bearing ore under a microscope you will notice that the barren rock is joined with the valuable mineral, to separate the two the rock must be ground until there isn’t very much host rock left attached to the mineral.
How hard this will be to accomplish depends very much on the type and the amount of mineral present in the ore. Through METALLURGICAL LAB testing it will be determined exactly to what size the ore must be ground to be the most effective in the recovery process. The mineral sizing will be expressed in either MICRONS or plus or minus a SCREEN MESH SIZE.