Accessory opaque minerals include base metal sulphides, sulphosalts, magnetite, rutile, leucoxene and gold-silver tellurides. Microscopically visible particles of free gold are rare. Free Gold Free, visible gold in the oxide zone has been identified locally as spongy, irregular particles from 50 m to 1.5 mm in size, with a fineness ranging between 965 and 992. However, most of the gold in the oxide zone is sub-microscopic in size. In the sulphide zone, free gold is extremely rare.
Visible gold is associated with quartz.
Most of the gold probably occurs in pyrite in particles less than 0.01 m in size, and to a lesser extent in chalcopyrite and marcasite. Pyrite Pyrite is the dominant sulphide throughout the mineralised zone in all alteration types with marcasite as an accessory sulphide. Both appear to have replaced pyrrhotite in part. In phyllic altered rocks, pyrite has been observed as coalesced strings of single crystals replacing breccia matrix, as veinlets up to 5 mm wide, and as spheroidal particles in quartz veins. Pyrite may contain inclusions of quartz, rock flour, magnetite, bornite and chalcopyrite.