Complex sentence: Caribou and its silver mines were completely deserted by the time 19-year old geology student Tom Hendricks saw it in 1970, but Hendricks became convinced that the silver mines at Caribou could make a profit, and has made the mines his life work.
Split into simpler sentences: Caribou and its silver mines were completely deserted by the time 19-year old geology student Tom Hendricks saw it in 1970. But Hendricks became convinced that the silver mines at Caribou could make a profit, and has made the mines his life work.