Fig. 13

Photomicrographs of the different opaque minerals: (a) Pyrite (Py) occurred as domal form or (b) as cavity filling within silicified granite. (c) Partially altered Pyrite and (d) completely altered pyrite to goethite (Gth). (e) Chalcopyrite occurs as an anhedral crystal. (f) Arsenopyrite (As) disseminates in the prismatic crystal of feldspar. (g) Marcasite (Mar) appears as anhedral crystals with coin form. (h) Magnetite occurs as euhedral with bipyramidal form. (i, j) Magnetite crystals are replaced partially or completely with hematite (martitization).