The Mercury presence in the Carson river is primarily introduced in to the river through sediment deposition resulting from mine tailings during the Comstock Lode. These tailings were attributed to the mining process that settlers used in the 1850s to recover silver and gold. This process is known as mercury amalgamation. Mercury amalgamation has been used in the process of mining precious metal since the Middle Ages. Mercury amalgamation is accomplished by pulverizing the ore and covering it with mercury using drums or tables. Once the mercury binds to the gold or silver it is separated from the barren soil to a retorting vessel where the mercury is vaporized and condensed off of the amalgam. During the Comstock Lode a new, Washoe "hot-pan" amalgamation, process was created specifically to treat Nevada ore in 1861. Washoe "hot pan" mining used a cast iron pan with the soil mixture, mercury, sulfuric acid, and other materials to remove the precious metals.