Modes of Au, Pt, and Pd occurrence in arsenopyrite from the Natalkinskoe deposit, NE Russia

Abstract

Pioneering data obtained by studying arsenopyrite from the Natalkinskoe deposit indicate that the mineral contains equidistributed Au, Pt, and Pd in two major non-mineral modes: structural and surface-bound. High Au, Pt, and Pd concentrations in the arsenopyrite are proved to be related to the surface-bound mode. No individual Pt and Pd minerals were detected, while Au occurs mostly in the form of native metal. Variably sized native Au grains (mostly small ones) form aggregates with arsenopyrite and quartz and occur in them as small inclusions. The situation with Pt and Pd is different: arsenopyrite is likely the main concentrator of the elements. Gold-bearing arsenopyrite seems to accommodate all admixtures according to a single mechanism, in which an active role is played by the surface of crystals of the mineral and its surface defects. In view of this, it is possible to recover refractory gold without disintegrating the structure of the mineral, a fact that should be taken into account at, for example, processing ores containing sulfides, for instance, arsenopyrite.