Apart from visible gold, I don't think there is any reliable...

Apart from visible gold, I don't think there is any reliable indications of gold content based on visuals, was just "the right rocks" supposedly. See ASX:BUX announcement for their copper wolf drilling. Similar copper porphyry system as we are looking for here except it was Cu-Mo not Cu-Au and reported chalcopyrite % before assays. If it is a fertile Cu-porphyry I'd assume copper would be present as visual Chalcopyrite throughout the core. They would be obligated to report that based off latest ASX rules.