Many mines around Australia and overseas use the improved Jameson flotation cell, also developed in Australia. Ground-up ore, water and special chemicals are mixed together and constantly agitated in banks of flotation cells. Air is blown through the mixture in each cell and fine silver bearing galena particles stick to the bubbles, which rise to form a froth on the surface of the cell. The tailings sink to the bottom of the cell and are removed. The froth is skimmed off and the resulting silver-lead sulphide concentrate may assay 800 grams to 1 kilogram of silver per tonne of concentrate.
Silver is recovered when crude lead is refined to high purity.
Crude lead is re-melted and antimony and other impurities removed. The molten lead is then poured into a large upright container called a 'kettle' where it plunges through a molten zinc metal layer floating on top of molten lead. The crystals float to the surface and re-dissolve in the zinc layer. Most of the silver output from Mt Isa and Hilton mines is in lead concentrates, which are smelted to lead bullion at Mt Isa. The bullion is exported to the United Kingdom for refining and silver extraction.