Scientists Discover Air Pollution in Peru From Almost 500 Years Ago

Gabrielli said the Inca refined silver through a smelting technique that used huyara, or small clay furnaces. This process was fairly inefficient, and only allowed the Inca to mine small amounts of silver. When the Spanish arrived, they introduced a more efficient refining technique called mercury amalgamation. This process uses liquid mercury to extract silver from various ores. With a more efficient refining technique, the Spanish were able to mine larger quantities of silver ore. This in turn produced larger amounts of metallic dust, which was carried in the air to places like the Quelccaya Ice Cap in Peru, where the team took their ice core sample.
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