How does Silver form?

Many of the metals that are so important to us, such as gold, silver, copper, lead, zinc, are present in the Earth's crust only in very small amounts. Silver is present as only about 5 parts in a million. (Imagine a million Smarties and only 5 of them are silver.)

diagram of the formation of silver

Apart from gold, which is special, the other metals form compounds with sulphur, called sulphides. Deep in the Earth's crust, where it is very hot, salty water (called brine) circulates and dissolves these metals, collecting them up and concentrating them in the hot brine. The brine can be as hot as 350C. Sometimes, on the sea floor, this brine comes up through the surface out of holes we call vents. When the hot brine comes into contact with the cold sea water the metal sulphides cannot stay dissolved and precipitate onto the sea floor as various minerals. Copper is precipitated as chalcopyrite (copper sulphide), lead as galena (lead sulphide), and zinc as sphalerite (zinc sulphide). Silver precipitates as a mixture with the other sulphides. The sulphides build up on the seafloor around the vents, like chimneys. Because the water appears black with all the minerals in it, the chimneys are called Black Smokers (mpeg movie).

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Minerals Downunder Iron Contents