About Silver
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. Its main use then was as
a precious metal — as currency, ornaments and jewelry,
and as utensils (hence the term silverware). Today, in addition
to such uses, it is found in photographic film, electrical
contacts, and mirrors. Elemental silver is also used to
catalyze chemical reactions.
Silver
has certain anti-microbial 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 due known as argyria.
In
folklore, silver is able to repel vampires and kill werewolves.
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, though it was used in the electromagnets
used for enriching uranium during World War II (mainly because
of the wartime shortage of copper).
Pure
silver has the highest thermal conductivity, whitest color,
the highest optical reflectivity, although aluminium slightly
outdoes it in parts of the visible spectrum, and is a poor
reflector of ultraviolet light). Silver also has the lowest
contact resistance of any metal. Silver halides are photosensitive
and are remarkable for the effect of light upon them. This
metal is stable in pure air and water, but does tarnish
when it is exposed to ozone, hydrogen sulfide, or air containing
sulfur. The most common oxidation state of silver is +1
(for example, silver nitrate, AgNO3); a few +2 (for example,
silver(II) fluoride; AgF2) and +3 compounds (for example,
silver(III) persulfate; Ag2(SO5)3) are also known.
History
of Silver
Silver has been known since ancient times. It is mentioned
in the book of Genesis, and slag heaps found in Asia Minor
and on the islands of the Aegean Sea indicate that silver
was being separated from lead as early as the 4th millennium
BC.
Silver
has been used for thousands of years for ornaments and utensils,
for trade, and as the basis for monetary systems. Its value
as a precious metal was long considered second only to gold.
In Ancient Egypt and Medieval Europe, it was often more
valuable than gold.
Judas
Iscariot is infamous for having, according to the New Testament,
taken a bribe of thirty pieces of silver from religious
leaders in Jerusalem to turn Jesus Christ over to the Romans.
Associated
with the moon, as well as with the sea and various lunar
goddesses, the metal was referred to by alchemists by the
name luna. One of the alchemical symbols for silver is a
crescent moon with the open part on the left (see picture,
left).
The
metal mercury was thought of as a kind of silver, though
the two elements are chemically unrelated; its Latin and
English names, hydrargyrum ("watery silver") and
quicksilver, respectively, reflect this history.
In
heraldry, the argent, in addition to being shown as silver
(this has been shown at times with real silver in official
representations), can also be shown as white. Occasionally,
the word "silver" is used rather than argent;
sometimes this is done across-the-board, sometimes to avoid
repetition of the word "argent" in blazon.
Europeans
found a huge amount of silver in the New World in Zacatecas
and Potosí, which triggered a period of inflation
in Europe. The conquistador Pizarro was said to have resorted
to having his horses shod with silver horseshoes due to
the metal's abundance, in contrast to the relative lack
of iron in Peru. Silver, which was extremely valuable in
China, became a global commodity, contributing to the rise
of the Spanish Empire. The rise and fall of its value affected
the world market.
The
Rio de la Plata was named after silver (in Spanish, plata),
and in turn lent the meaning of its name to Argentina.
Silver
mining was a driving force in the settlement of western
North America, with major booms for silver and associated
minerals (primarily lead) in the galena ore silver is most
commonly found in. Notable "silver rushes" were
in Colorado, Nevada, Cobalt, Ontario , California and the
Kootenay region of British Columbia, notably in the Boundary
and "Silvery Slocan". The largest silver ore deposits
in the United States were discovered at the Comstock Lode
in Virginia City, Nevada, in 1859. In northern Idaho the
world-famous Sunshine Mine, the richest silver mine in American
history, has had more than 350 million ounces of production
over the past century.At the time of its closure in early
2001, the Sunshine was producing at a rate of over three
million ounces of silver per year at an average grade of
approximately twenty ounces per ton. The prior operator
last estimated the mine reserves at 26.75 million ounces
of silver, 10.36 million pounds of copper and 7.05 million
pounds of lead (or approximately 28.85 million ounces of
silver-equivalent), as well as an additional resource of
159.66 million ounces of silver.
Silver Production
Silver is found in native form, combined with sulfur, arsenic,
antimony, or chlorine and in various ores such as argentite
(Ag2S) and horn silver (AgCl). The principal sources of silver
are copper, copper-nickel, gold, lead and lead-zinc ores obtained
from Canada, Mexico (historically Batopilas), Peru, Australia
and the United States.
This
metal can also produced during the electrolytic refining
of copper and by application of the Parkes process on lead
metal obtained from lead ores that contain small amounts
of silver. Commercial grade fine silver is at least 99.9%
pure silver and purities greater than 99.999% are available.
Mexico is the world's largest silver producer. According
to the Secretary of Economics of Mexico, it produced 80,120,000
troy ounces (2492 metric tons) in 2000, about 15% of the
annual production of the world.
