LIBERATION OF ACCESSORY MINERALS FROM VARIOUS ROCK TYPES BY ELECTRIC-PULSE DISINTEGRATION-METHOD AND APPLICATION

Electric-pulse disintegration is a mineral separation technique that l iberates all mineral grains from any igneous or metamorphic rock irres pective of its lithology or grain-size distribution. The normal mechan ical crushing of whole-rock samples is replaced by the rending effect of an explosion, which is produced by applying an electric current fro m a high-voltage power source. A voltage greater than the 100 kV neces sary for the electrical breakdown of rock samples is achieved by using capacitors that are charged in parallel but discharged in series. The sample sits in a water bath and the rapid distribution of electric pu lses through the sample leads to explosion, which occurs preferentiall y along grain boundaries (zones of weakness). As a result, individual, undamaged mineral grains can be recovered in their original shape and form regardless of grain size. The electric-pulse disintegration meth od has wide potential application in geoscience and industry. Examples are given of the liberation and concentration of economically and sci entifically important accessory minerals from different rock types. Th e examples considered are the recovery of diamonds from two types of n on-kimberlitic host rock and of platinum-group minerals associated wit h chromitites and sulphides from mafic intrusions.