A
precious metal is a rare metallic chemical element of high economic
value.
Chemically, the precious metals are less reactive than most elements,
have high luster, and have higher melting points than other metals.
Historically, precious metals were important as currency, but are
now regarded mainly as investment and industrial commodities. Gold,
silver, platinum and palladium each have an ISO 4217 currency code.
The best-known precious metals are gold and silver. While both have
industrial uses, they are better known for their uses in art, jewellery,
and coinage. Other precious metals include the Platinum group metals:
ruthenium, rhodium, palladium, osmium, iridium and platinum, of which
platinum is the most widely traded.
The demand for precious metals is driven not only by their practical
use, but also by their role as investments and a store of value. Palladium
is, as of March 11, 2007, valued at $350.00 USD per ounce, which is
slightly above half the price of gold ($650.20 USD/ounce), and platinum
($1210.50 USD/ounce) at around twice that of gold. Silver is substantially
less expensive ($12.82 USD/ounce) than these metals, presently at
about 1/50 the price of gold, but is often traditionally considered
a precious metal for its role in coinage and jewellery. Rhodium though
is the most expensive of the precious metals with prices as high as
$6200.00 USD per ounce (as of December 29, 2006).
Gold:
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Silver
is a chemical element with the symbol Ag (Latin: argentum). A soft
white lustrous transition metal, it has the highest electrical and
thermal conductivity for a metal, and occurs as a free metal, and
in minerals such as argentite and chlorargyrite. Most silver is produced
as a by-product of copper, gold, lead, and zinc mining.
Silver has been known since antiquity. It has long been valued as
a precious metal and used in currency, ornaments and jewelry, as well
as utensils (hence the term silverware). Today, it is also used in
photographic film, electrical contacts, and mirrors. Elemental silver
is also used to catalyze chemical reactions.
Silver has certain antimicrobial activity. In the past, dilute solutions
of silver nitrate were used as disinfectants, though this has been
supplanted by other treatments. In alternative medicine, there has
been increasing interest in the use of colloidal silver as remedies
for a wide range of ailments, though these claims are disputed. The
consumption of large amounts of silver can lead to a darkening of
the skin known as argyria.
Platinum
is a chemical element in the periodic table that has the symbol Pt
and atomic number 78. A heavy, malleable, ductile, precious, grey-white
transition metal, platinum is resistant to corrosion and occurs in
some nickel and copper ores along with some native deposits. Platinum
is used in jewelry, laboratory equipment, electrical contacts, dentistry,
and automobile emissions control devices.
Palladium
is a chemical element with symbol Pd and atomic number 46. It is a
rare silver-white transition metal of the platinum group, resembling
platinum chemically. It was discovered in platinum ores in 1803, and
named after the asteroid Pallas by William Hyde Wollaston.
Palladium is usually found as a free metal, alloyed with others in
the platinum group. It is commercially extracted from copper-nickel
ores. Palladium has a great affinity for hydrogen, being able to absorb
900 times its own volume of the gas. Palladium metal and its complexes
are often used in catalysis such as in catalytic converters on cars,
palladium on carbon used in organic chemistry, and other coupling
reactions. As a precious metal, it is sometimes used in jewelry.
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of: www.wikipedia.org