Wear of Diamond: An Experimental Study and Field Evidence

Abstract

Wear of diamond and kimberlite indicator minerals (pyrope, Mg-ilmenite, and chromite) has been investigated in experiments. The minerals were subjected to mechanical action using an ultrasonic dispersant. Over the 132 h of the total duration of experiment, magnesian ilmenite and chromite were nearly eliminated, while pyrope became well rounded and lost about 65 % of its initial weight. In contrast, diamond acquired a very weak signature of wear restricted to sharp edges and tips, and no weight loss was recorded. In the nature, minerals, including diamond, are most strongly abraded in coastal environments being exposed to the action of waves in the swash zone. Therefore, slightly abraded placer diamond may coexist with strongly rounded pyrope, but the assemblages may lack Mg-ilmenite, which becomes worn almost to zero. As one may infer by extrapolation, all indicator minerals except diamond must be eliminated from placers where the wear of diamond is of a medium degree.