Potosí was founded in 1545 as a mining town near Cerro Rico, a mountain which contained enormous quantities of silver ore. By 1570, a new process using mercury amalgamation was developed which allowed the silver ores of the mountain to be profitably exploited using forced labor in hazardous conditions. By the early 1600s, Potosí had a population of 160,000. In 1572, the first National Mint of Bolivia was constructed to process the smelted silver into real coins, which were then shipped to Arica on the western coast of South America and thereon to the Spanish Main and points around the world. The minted coins were to have a silver content of 93 parts per 100, as decreed by King Philip IV of Spain in 1642.