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Gold
| Silver | Platinum
SILVER
Silver usually occurs in massive form as nuggets or
grains, although it may also be found in wiry, dendritic (tree-like)
aggregates. Silver is a very ductile and malleable (slightly harder than
gold) univalent coinage metal with a brilliant white metallic luster that
can take a high degree of polish. It has the highest electrical conductivity
of all metals, even higher than copper, but its greater cost and
tarnishability has prevented it from being widely used in place of copper
for electrical purposes. On exposure to oxygen in the air |
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| a black layer of silver oxide readily forms, tarnishing
the surface. Because of this, and the fact that it is too soft to be used in
most jewellery in its pure form, silver is often alloyed with other metals or given a covering layer of gold. Electrum, an alloy of
gold and silver in use since the time of the Ancient Greeks, contains 20-25
percent silver. Sterling silver contains 92Yz per cent or more pure silver
(and usually some copper), and Britannia silver has a silver content of 95
per cent or more. Both alloys are used as standards to define silver
content. |
Silver Mirror Frame
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OCCURRENCE
Most silver is a by product of lead mining, and is often
associated with copper. The main silver mining areas of the world are South
America, the USA, Australia, and the former USSR. The greatest single
producer of silver is probably Mexico, where silver has been mined from
about AD 1 500 to the present day. The finest native silver, which occurs
naturally in the shape of twisted wire, is from Kongsberg, Norway. |
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| Electrical and electronic products, which need silver's
superior conductivity, even when tarnished. For example,
printed circuits are made using silver paints, and computer
keyboards use silver electrical contacts. Silver (silver
cadmium oxide) is also used in high voltage contacts because
it can minimize any arcing. |
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Mirrors which need superior
reflectivity for visible light are made with silver as the
reflecting material in a process called silvering. Common
mirrors are backed with aluminium. Silver has been coined to produce money since 700 BC by
the Lydians, in the form of electrum. Later, silver was
refined and coined in its pure form. The words for "silver"
and "money" are the same in at least 14 languages.
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Silver currency coin
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Silver flute |
Silver is also used in high end musical instruments for
getting higher tone quality. Siver flute (right) is such an example. Silver
saxophone, silver trumpets, silver harmonicas are other examples. silver
strings are used in guitar and violin for higher quality sound. |
| Silver had beneficial healing and anti-disease
properties, and the Phoenicians used to store water, wine,
and vinegar in silver bottles to prevent spoiling. In the
early 1900s people would put silver dollars in milk bottles
to prolong the milk's freshness. Silver compounds were used
successfully to prevent infection in World War I before the
advent of antibiotics. |
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The metal is chosen for its beauty in the manufacture of
jewelry and silverware, which are traditionally made from
the silver alloy known as Sterling silver, which is 92.5%
silver and usually alloyed with copper. The name of United
Kingdom monetary unit 'Pound' originally had the value of
one troy pound of sterling silver. Sterling silver is
an alloy of silver containing 92.5% pure silver and 7.5%
other metals, usually copper. The minimum millesimal
fineness is 925. Fine
silver (99.9% pure) is generally too soft
for producing large functional objects, and
in Sterling the silver is usually alloyed
with copper to give strength whilst
preserving the ductility of the silver and a
high precious metal content.
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Natural Gemstones |
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