There used to be a platnium mine up near Phelan Creek about mile 201 of the Richardson north of Paxon. It is easily seen as the entire area was worked well up by the glacier. All gold in that area was found on the west side of the mountain range. Very little was found on the eastern slopes.
What to look for. Haven't found any, thought the stuff I had was silver. But: It is silver-gray in color, medium heavy, ductile, no clevage, could be slightly magnetic and not discolored when exposed to air. Scales, flakes and sometimes nuggets.
I might suggest if you looking:
Rock and Minerals by Simon and Schuster
Hankbook for The Alaskan Prospector by Ernest Wolff