Indians moved around to relocate when food was scarce, then many villages died off in epidemics of diseases brought by the Europeans. Spanish symbols in the area, seemed like a cache site when I dowsed it.....hopefully the treasure never got recovered. Now as for the silver, there is very little difference between a silver vein with rich ore pockets and a cave/tunnel containing a silver cache. The reason why, the entire area of the cave/tunnel or connecting caves, gives off a signal because it contains a treasure. Any openings to a sealed room or entrances leading in, also produce a response when dowsed. The first 1-2 blue Xs I marked, did seem to be strong enough for to be either a cache or a pocket in a vein. That would mean a cache plus an opening marked, if this was a cave/tunnel. There was a little trace gold in spots of the map, reason for me thinking it must be a silver vein.