Also, if you look closely, trade goods are generated as personal possessions for the Hunter/Woodsman/Tribesman and Merchant/Trader individual categories, though again, how this relates to Earthmaster society remains anyone's guess.
Why did the earthmasters come to Harn? To colonies the world my guess. That means building structures, farming, exploration.
And a lot of things didn't survive the ravages of time and if they did some of them just might be underground just waiting to be found.
If you made up a earthmaster Trade Goods table would you include the possibility of finding all metals found on the periodic table of our world in a earthmaster treasure table?