People with certain skills and high exploration/perception ought to be able to create maps with legends, particularly showing (in red density) the quality of local resources.
This would show up ONLY if a cartographer maps out a local area with these skills. The same should happen with cave systems to allow for players to prospect more efficiently as they map the cave and use the prospect skill it would be a little like minesweeper, to players have something visual to go on to better find the mines.