Gossan - Outcroppings.

Rusty iron-oxides come from deteriorating iron bearing sulfide minerals of chalcopyrite and pyrite. Inhabitants of massive unstained quartz veins, "iron hat blows_out," is evidence that might well be searched for gossans and associated veins of the region that appear to be of iron or copper stained. Gossans, outcroppings, with the smattering of sulfides are realgan, orpiment or cinnabar are good signals for searching the region more closely for gold occurrences and particles. Gold is most evident in quartz veins and co-mingles with ankerite and calcite as well. When tetrahedite exists, both gold 'n silver will be found shot thrue the associated vein structure. Should manganese (and its oxides) exist, gold will be barren thrue the mineral substance, but silver will be in abundance. Where gold is found to exist with iron-oxides, silver is anti-iron and is devoid of being co-existent.

(Reference: Where to Find Arizona's Placer Gold)