The weapons that don't use precious metals don't use precious metals for a reason. Unless you have better ideas. Dwemer is essentially never used with any other metal on the same object. Steel is supposed to represent strength & functionality, adding a precious metal would take away from that. Besides, I think most players (including myself) would be annoyed with needing to use gold or silver to forge a sword out of steel. Besides, if steel was paired with a precious metal it would be less different than the other metals which are paired.
Orichalcum should be cruder? How & Why? It isn't paired with a precious metal, like steel, in order to make it look more basic & functional.
So, there is precious metal in iron longsword? Also - I said dwemer is fine as it is, since it's, duh, dwemer. If I figure how to extract textures from Skyrim, I'll try to show it ingame, because I can't really explain it in words :\