Silver is a fairly soft metal that is highly malleable. It occurs widely in association with copper ores and is obtained mainly as a by-product of copper mining. It is also produced as a by-product of gold, lead, nickel and zinc mining. The world’s largest deposits of silver are found in Bolivia, but there are other countries that produce more silver. The leading world producers are Mexico, Canada, the US, Russia, Peru. Australia and Japan.
Silver can easily be drawn out into thin wire or worked into different shapes. It is heavy, with a density of 10.49g per cubic cm at 20º. It is the best metal for conducting heat and electricity, which is why is its used in the construction industry. It is also used in jewelry because of its ability to be polished to a high luster.
In its purest form, silver is too soft for most applications. It is generally used in the form of alloys, which are not only harder than silver, but are also more resistant to tarnishing. Pure silver is used mainly in the manufacture of mirrors and in the production of formaldehyde. Sterling silver is the most common alloy of silver. This contains 92.5% silver and 7.5% copper. This is used to make silverware, jewelry and ornaments.
Silver has been used for ornamental purposes since early times. The earliest known reference to silver occurred in Egyptian writings in about 3000 B.C. The discovery of silver in the New World led to the exploration of many countries, such as those in South America in search of the precious metal.
There are several different methods used to extract silver from other ores. Electrolysis is one of these methods in which slime accumulates on the positive electrodes. This slime contains silver and after the process is complete, the slime is removed and the silver extracted. In the cyanide process, the silver ore is added to a solution of sodium cyanide that contains an oxidizing agent, such as dissolved oxygen. Another process is the Parks process in which pieces of zinc are stirred into molten lead. Since zinc readily forms an alloy with silver, any silver present in the lead dissolves in the zinc and rises to the top of the molten lead, from which it is removed.