1 (minimum): Fantie (common iron)
Grade 2: iron and steel (smelted and purified iron)
Grade 3: Meteorites (such as moire iron, broken iron, red star meteorite and angelica dahurica meteorite) belong to alien meteorites, some of which are better than grade 5 iron.
Grade 4: Ironmaking (red phosphorus steel, Montenegro edible gold iron, latosolic red darksteel, Thunder diamond steel) is specialized in smelting.
Grade 5: Tie Bao (refined stone steelmaking, void stone, moire iron) is a real natural treasure.
Grade 6: Fairy iron (fairy marble, clam-patterned black iron) is a rare fairy treasure in the world.