The world's most prolific silver mines are in Peru, Chile, Bolivia, Mexico, Australia and the United States. Serbia and China also produce substantial amounts of silver. Although miners occasionally uncover nuggets of pure silver, most silver deposits develop inside copper and lead ore. Pure silver is the result of complex mechanical, thermal and chemical refinement techniques that separate it from other elements in the ore.
Silver extraction begins with chemical flotation separation. This process involves pulverizing ore, mixing it with hydrophobic chemicals and dumping the slurry into a tank of water. The chemicals bond preferentially with metal particles and form tiny air bubbles around them. The metals float to the surface of the separation tank, and the rest of the crushed ore sinks to the bottom. Refinery workers collect the concentrated metal particles and proceed to the next step in the silver extraction process.
Refiners use several methods to extract silver from concentrated ore. Refiners choose the approach that is best suited to the composition and quantity of the ore. For example, electrolysis is the most popular method of extracting silver from copper. The most efficient way to extract silver from lead ore involves adding zinc to the molten lead. Zinc attracts the silver atoms suspended in the lead but does not mix with the lead itself. This creates two distinct layers of molten metal. After siphoning the lead layer into another tank, smelters increase the temperature of the zinc mixture until the zinc evaporates, leaving the silver behind.