 When new areas were explored, it was usually the gold (placer and then lode) and then silver that were taken into possession and extracted first.Other metals would often wait for railroads or canals, as coarse gold dust and nuggets do not require smelting and are easy to identify and transport.In the early 20th century, the gold and silver rush to the western United States also stimulated mining for coal as well as base metals such as copper, lead, and iron.