Gold
is a chemical element with the symbol Au (from the Latin aurum) and
atomic number 79. It is a highly sought-after precious metal which,
for many centuries, has been used as money, a store of value and in
jewelery. The metal occurs as nuggets or grains in rocks, underground
"veins" and in alluvial deposits. It is one of the coinage
metals. It is a dense, soft, shiny, yellow metal, and is the most
malleable and ductile of the known metals.
Gold forms the basis for a monetary standard used by the International
Monetary Fund (IMF) and the Bank for International Settlements (BIS).
Its ISO currency code is XAU. Modern industrial uses include dentistry
and electronics, where gold has traditionally found use because of
its good resistance to oxidative corrosion.
Chemically, gold is a trivalent and univalent transition metal. Gold
does not react with most chemicals, but is attacked by chlorine, fluorine,
aqua regia and cyanide. Gold dissolves in mercury, forming amalgam
alloys. In particular, gold is insoluble in nitric acid, which will
dissolve most other metals. Nitric acid has long been used to confirm
the presence of gold in items, and this is the origin of the colloquial
term "acid test," referring to a gold standard test for
genuine value.
Characteristics
Gold is the most malleable and ductile metal; a single gram can be
beaten into a sheet of one square meter, or an ounce into 300 square
feet. Gold readily forms alloys with many other metals. These alloys
can be produced to increase the hardness or to create exotic colors.
Adding copper yields a redder metal, iron blue, aluminium purple,
platinum white, and natural bismuth and silver alloys produce black.
Native gold contains usually eight to ten percent silver, but often
much more - alloys with a silver content over 20% are called electrum.
As the amount of silver increases, the color becomes whiter and the
specific gravity becomes lower.
Gold is a good conductor of heat and electricity, and is not affected
by air and most reagents. Heat, moisture, oxygen, and most corrosive
agents have very little chemical effect on gold, making it well-suited
for use in coins and jewelry; conversely, halogens will chemically
alter gold, and aqua regia dissolves it by virtue of the elemental
chlorine generated by this acid mixture.
Common oxidation states of gold include +1 (gold(I) or aurous compounds)
and +3 (gold(III) or auric compounds). Gold ions in solution are readily
reduced and precipitated out as gold metal by adding any other metal
as the reducing agent. The added metal is oxidized and dissolves allowing
the gold to be displaced from solution and be recovered as a solid
precipitate.
Recent research undertaken by Sir Frank Reith of the Australian National
University shows that microbes play an important role in forming gold
deposits, transporting and precipitating gold to form grains and nuggets
that collect in alluvial deposits.[1]
High quality pure metallic gold is tasteless, in keeping with its
resistance to corrosion (it is metal ions which confer taste to metals).[2]
Gold is non-toxic if consumed, and is used as food decoration in the
form of gold leaf.
In addition, gold is very dense, a cubic meter weighing 19300 kg.
By comparison, the density of lead is 11340 kg/m3, and the densest
element, Iridium, is 22650 kg/m3.
[edit] Applications
[edit] As the metal
Medium of monetary exchange. Pure gold is too soft for ordinary use
and is typically hardened by alloying with silver, copper, or other
metals. In various countries, gold, and its many alloys, are most
often used in jewelry, coinage and as a standard for monetary exchange.
The gold content of jewellery alloys is measured in carats (k), pure
gold being designated as 24k. It is, however, more commonly sold in
lower measurements of 22k, 18k, 14k and 10k. A lower "k"
indicates a higher percent of silver, copper or other base metals
in the alloy, copper being the more commonly used base metal. Fourteen
carat gold-copper alloy is nearly identical in color to certain bronze
alloys, and both may be used to produce police and other badges. Eighteen
carat gold containing 25% copper is found in some antique jewelry
and has a distinct, though not dominant, copper cast, creating an
attractively warm color. When alloyed with silver alone, 18 carat
gold appears yellow-green in color. White 18 carat gold can be made
with 17.3% nickel, 5.5% zinc and 2.2% copper and is silver in appearance.
Nickel is toxic, however, and its release from nickel white gold is
controlled by legislation in Europe. Alternative white gold alloys
are available based on palladium, silver and other white metals (World
Gold Council), but the palladium alloys are more expensive than those
using nickel. High-carat white gold alloys are far more resistant
to corrosion than are either pure silver or sterling silver.
Gold coins intended for circulation prior to the 1930s were typically
22k, for hardness. Modern collector/investment bullion coins (which
do not require good mechanical wear properties) are typically 24k,
although the American Gold Eagle continues to be made at 22k. Until
recently, the Canadian Gold Maple Leaf coin contained the highest
purity gold of any popular bullion coin, at 99.99% (.9999 fine). However,
several other 99.99% pure gold coins are currently available, including
Australia's Gold Kangaroos (first appearing in 1986 as the Australian
Gold Nugget, with the kangaroo theme appearing in 1989), the several
coins of the Australian Lunar Calendar series, and the Austrian Philharmonic.
In 2006, the U.S. Mint began production of the American Buffalo gold
bullion coin also at 99.99% purity.
Other
uses for Gold:
"
In medieval times, gold was often seen as beneficial for the health,
in the belief that something that rare and beautiful could not be
anything but healthy. Even some modern esotericists and forms of alternative
medicine assign metallic gold a healing power. Some gold salts do
have anti-inflammatory properties and are used as pharmaceuticals
in the treatment of arthritis and other similar conditions. However,
only salts and radioisotopes of gold are of pharmacological value,
as elemental (metallic) gold is inert to all chemicals it encounters
inside the body.
" Gold leaf, flake or dust is used on and in some gourmet foodstuffs,
notably sweets and drinks as decorative ingredient.[3] Gold flake
was used by the nobility in Medieval Europe as a decoration in foodstuffs
and drinks, in the form of leafs, flakes or dust, either to demonstrate
the host's wealth or in the honest belief that something that valuable
and rare must be beneficial for one's health.
" Gold solder is used for joining the components of gold jewellery
by high-temperature hard soldering or brazing. If the work is to be
of hallmarking quality, gold solder must match the carat weight of
the work, and alloy formulae are manufactured in most industry-standard
carat weights to colour match yellow and white gold. Gold solder is
usually made in at least three melting-point ranges referred to as
Easy, Medium and Hard. By using the hard, high-melting point solder
first, followed by solders with progressively lower melting points,
goldsmiths can assemble complex items with several separate soldered
joints.
" Goldwasser (German: "Goldwater") is a traditional
herbal liqueur produced in Gdansk, Poland and Schwabach, Germany and
contains flakes of gold leaf. There are also some expensive (~1000$)
cocktails which contain flakes of gold leaf. However, since metallic
gold is inert to all body chemistry, it adds no taste nor has it any
other nutritional effect and leaves the body unaltered.
" Dentistry. Gold alloys are used in restorative dentistry, especially
in tooth restorations, such as crowns and permanent bridges. The gold
alloys' slight malleability facilitates the creation of a superior
molar mating surface with other teeth and produces results that are
generally more satisfactory than those produced by the creation of
porcelain crowns. The use of gold crowns in more prominent teeth such
as incisors is favored in some cultures and discouraged in others.
" Gold can be made into thread and used in embroidery.
" Gold is ductile and malleable, meaning it is able to be drawn
into very thin wire and can be beaten into very thin sheets known
as gold leaf.
" Gold produces a deep, intense red color when used as a coloring
agent in glass.
" In photography, Gold toners are used to shift the colour of
silver bromide black and white prints towards brown or blue tones,
or to increase their stability. Used on sepia-toned prints, gold toners
produce red tones. Kodak publish formulae for several types of gold
toners, which use gold as the chloride (Kodak, 2006)
" Electronics. The concentration of free electrons in gold metal
is 5.90×1022 cm-3. Gold is highly conductive to electricity,
and has been used for electrical wiring in some high energy applications
(silver is even more conductive per volume, but gold has the advantage
of corrosion resistance). For example, gold electrical wires were
used during some of the Manhattan Project's atomic experiments, but
large high current silver wires were used in the calutron isotope
separator magnets in the project.
o Though gold is attacked by free chlorine, its good conductivity
and general resistance to oxidation and corrosion in other environments
(including resistance to non-chlorinated acids) has led to its widespread
industrial use in the electronic era as a thin layer coating electrical
connectors of all kinds, thereby ensuring good connection. For example,
gold is used in the connectors of the more expensive electronics cables,
such as audio, video and USB cables. The benefit of using gold over
other connector metals such as tin in these applications, is highly
debated. Gold connectors are often criticized by audio-visual experts
as unnecessary for most consumers and seen as simply a marketing ploy.
However, the use of gold in other applications in electronic sliding
contacts in highly humid or corrosive atmospheres, and in use for
contacts with a very high failure cost (certain computers, communications
equipment, spacecraft, jet aircraft engines) remains very common,
and is unlikely to be replaced in the near future by any other metal.
o Besides sliding electrical contacts, gold is also used in electrical
contacts because of its resistance to corrosion, electrical conductivity,
ductility and lack of toxicity.[4] Switch contacts are generally subjected
to more intense corrosion stress than are sliding contacts.
" Colloidal gold (Colloidal sols of gold nanoparticles) in water
are intensely red - colored, and can be made with tightly-controlled
particle sizes up to a few tens of nm across. Colloidal gold is used
in research applications in medicine, biology and materials science.
The technique of immunogold labeling exploits the ability of the gold
particles to adsorb protein molecules onto their surfaces. Colloidal
gold particles coated with specific antibodies can be used as probes
for the presence and position of antigens on the surfaces of cells
(Faulk and Taylor 1979). In ultrathin sections of tissues viewed by
electron microscopy, the immunogold labels appear as extremely dense
round spots at the position of the antigen (Roth et al. 1980). Colloidal
gold is also the form of gold used as gold paint on ceramics prior
to firing.
" Gold, or alloys of gold and palladium, are applied as conductive
coating to biological specimens and other non-conducting materials
such as plastics and glass to be viewed in a scanning electron microscope.
The coating, which is usually applied by sputtering with an argon
plasma, has a triple role in this application. Gold's very high electrical
conductivity drains electrical charge to earth, and its very high
density provides stopping power for electrons in the SEM's electron
beam, helping to limit the depth to which the electron beam penetrates
the specimen. This improves definition of the position and topography
of the specimen surface and increases the spatial resolution of the
image. Gold also produces a high output of secondary electrons when
irradiated by an electron beam, and these low-energy electrons are
the most commonly-used signal source used in the scanning electron
microscope.
" Many competitions, and honors, such as the Olympics and the
Nobel Prize, award a gold medal to the winner.
" As gold is a good reflector of both infrared and visible light,
it is used for the protective coatings on many artificial satellites
and in infrared protective faceplates in thermal protection suits
and astronauts' helmets.
" White gold (an alloy of gold with platinum, palladium, nickel,
and/or zinc) serves as a substitute for platinum.
" Green gold (a gold/silver alloy) is used in specialized jewelry
while gold alloys with copper are more standard, ranging from a pale
yellow with little copper all the way to a deep pink with more copper
(rose gold).
" Gold is used as the reflective layer on some high-end CDs.
" The isotope gold-198, (half-life: 2.7 days) is used in some
cancer treatments and for treating other diseases.
As
gold chemical compounds
Gold is attacked by and dissolves in alkaline solutions of potassium
or sodium cyanide, and Gold cyanide is used commercially in electro-plating
of gold onto base metals. Gold chloride (chloroauric acid) solutions
are used to make colloidal gold by reduction with citrate or ascorbate
ions. Gold chloride and gold oxide are used to make highly-valued
cranberry or red-coloured glass, which like colloidal gold sols contains
evenly-sized spherical gold nanoparticles.
History
Gold has been known and highly valued since prehistoric times. It
may have been the first metal used by humans and was valued for ornamentation
and rituals. Egyptian hieroglyphs from as early as 2600 BC describe
gold, which king Tushratta of the Mitanni claimed was "more plentiful
than dirt" in Egypt.[5] Egypt and Nubia had the resources to
make them major gold-producing areas for much of history. Gold is
also mentioned several times in the Old Testament, and is included
with the gifts of the magi in the first chapters of Matthew New Testament
The south-east corner of the Black Sea was famed for its gold. Exploitation
is said to date from the time of Midas, and this gold was important
in the establishment of what is probably the world's earliest coinage
in Lydia between 643 and 630 BC.
The European exploration of the Americas was fueled in no small part
by reports of the gold ornaments displayed in great profusion by Native
American peoples, especially in Central America, Peru, and Colombia.
Although the price of some platinum group metals can be much higher,
gold has long been considered the most desirable of precious metals,
and its value has been used as the standard for many currencies (known
as the gold standard) in history. Gold has been used as a symbol for
purity, value, royalty, and particularly roles that combine these
properties. Gold as a sign of wealth and prestige was made fun of
by Thomas More in his treatise Utopia. On that imaginary island, gold
is so abundant that it is used to make chains for slaves, tableware
and lavatory-seats. When ambassadors from other countries arrive,
dressed in ostentatious gold jewels and badges, the Utopians mistake
them for menial servants, paying homage instead to the most modestly-dressed
of their party.
There is an age-old tradition of biting gold in order to test its
authenticity. Although this is certainly not a professional way of
examining gold, the bite test should score the gold because gold is
considered a soft metal according to the Mohs' scale of mineral hardness.
The purer the gold the easier it should be to mark it. Painted lead
can cheat this test because lead is softer than gold (and may invite
a small risk of lead poisoning if sufficient lead is absorbed by the
biting).
Gold in antiquity was relatively easy to obtain geologically; however,
75% of all gold ever produced has been extracted since 1910.[6] It
has been estimated that all the gold in the world that has ever been
refined would form a single cube 20 m (66 ft) on a side (8000 m³).
The primary goal of the alchemists was to produce gold from other
substances, such as lead - presumably by the interaction with a mythical
substance called the philosopher's stone. Although they never succeeded
in this attempt, the alchemists promoted an interest in what can be
done with substances, and this laid a foundation for today's chemistry.
Their symbol for gold was the circle with a point at its center (?),
which was also the astrological symbol, the Egyptian hieroglyph and
the ancient Chinese character for the Sun (now ?). For modern attempts
to produce artificial gold, see gold synthesis.
During the 19th century, gold rushes occurred whenever large gold
deposits were discovered. The first major gold strike in the United
States occurred in a small north Georgia town called Dahlonega.[7]
Further gold rushes occurred in California, Colorado, Otago, Australia,
Witwatersrand, Black Hills, and Klondike.
Because of its historically high value, much of the gold mined throughout
history is still in circulation in one form or another.
Economic gold extraction can be achieved from ore grades as little
as 0.5 g/1000 kg (0.5 ppm) on average in large easily mined deposits.
Typical ore grades in open-pit mines are 1-5 g/1000 kg (1-5 ppm),
ore grades in underground or hard rock mines are usually at least
3 g/1000 kg (3 ppm) on average. Since ore grades of 30 g/1000 kg (30
ppm) are usually needed before gold is visible to the naked eye, in
most gold mines the gold is invisible.
Since the 1880s, South Africa has been the source for a large proportion
of the world's gold supply. Production in 1970 accounted for 79% of
the world supply, producing about 1,000 tonnes. However, production
in 2004 was 342 tonnes. This decline was due to the increasing difficulty
of extraction and changing economic factors affecting the industry
in South Africa.
The city of Johannesburg was built atop the world's greatest gold
finds. Gold fields in the Free State and Gauteng provinces are deep
and require the world's deepest mines. The Second Boer War of 1899-1901
between the British Empire and the Afrikaner Boers was at least partly
over the rights of miners and possession of the gold wealth in South
Africa.
Other major producers are Canada, United States and Australia. Mines
in South Dakota and Nevada supply two-thirds of gold used in the United
States. Siberian regions of Russia also used to be significant in
the global gold mining industry. Kolar Gold Fields in India is another
example of a city being built on the greatest gold deposits in India.
In South America, the controversial project Pascua Lama aims at exploitation
of rich fields in the high mountains of Atacama Desert, at the border
between Chile and Argentina. Today about one-quarter of the world
gold output is estimated to originate from artisanal or small scale
mining.[8]
After initial production, gold is often subsequently refined industrially
by the Wohlwill process or the Miller process. Other methods of assaying
and purifying smaller amounts of gold include parting and inquartation
as well as cuppelation, or refining methods based on the dissolution
of gold in aqua regia.
The world's oceans hold a vast amount of gold, but in very low concentrations
(perhaps 1-2 parts per billion). A number of people have claimed to
be able to economically recover gold from sea water, but so far they
have all been either mistaken or crooks. Reverend Prescott Jernegan
ran a gold-from seawater swindle in America in the 1890s. A British
fraud ran the same scam in England in the early 1900s.[9]
Fritz Haber (the German inventor of the Haber process) attempted commercial
extraction of gold from sea water in an effort to help pay Germany's
reparations following the First World War. Unfortunately, his assessment
of the concentration of gold in sea water was unduly high, probably
due to sample contamination. The effort produced little gold and cost
the German government far more than the commercial value of the gold
recovered. No commercially viable mechanism for performing gold extraction
from sea water has yet been identified. Gold synthesis is not economically
viable and is unlikely to become so in the foreseeable future.
The average gold mining and extraction costs are $238 per troy ounce
but these can vary widely depending on mining type and ore quality.
In 2001, global mine production amounted to 2,604 tonnes, or 67% of
total gold demand in that year. At the end of 2001, it was estimated
that all the gold ever mined totalled 145,000 tonnes.[10]
Price
Like other precious metals, gold is measured by troy weight and by
grams. When it is alloyed with other metals the term carat or karat
is used to indicate the amount of gold present, with 24 karats being
pure gold and lower ratings proportionally less. The purity of a gold
bar can also be expressed as a decimal figure ranging from 0 to 1,
known as the millesimal fineness, such as 0.995 being very pure.
The price of gold is determined on the open market, but a procedure
known as the Gold Fixing in London, originating in september 1919,
provides a daily benchmark figure to the industry. The afternoon fixing
appeared in 1968 to fix a price when US markets are open.
The high price of gold is due to its rare amount. Only three parts
out of every billion in the Earth's crust is gold. (0.000000003)
Historically gold was used to back currency; in an economic system
known as the gold standard, a certain weight of gold was given the
name of a unit of currency. For a long period, the United States government
set the value of the US dollar so that one troy ounce was equal to
$20.67 ($664.56/kg), but in 1934 the dollar was revalued to $35.00
per troy ounce ($1125.27/kg). By 1961 it was becoming hard to maintain
this price, and a pool of US and European banks agreed to manipulate
the market to prevent further currency devaluation against increased
gold demand.
On 17 March 1968, economic circumstances caused the collapse of the
gold pool, and a two-tiered pricing scheme was established whereby
gold was still used to settle international accounts at the old $35.00
per troy ounce ($1.13/g) but the price of gold on the private market
was allowed to fluctuate; this two-tiered pricing system was abandoned
in 1975 when the price of gold was left to find its free-market level.
Central banks still hold historical gold reserves as a store of value
although the level has generally been declining. The largest gold
depository in the world is that of the U.S. Federal Reserve Bank in
New York, which holds about 3% of the gold ever mined, as does the
similarly-laden U.S. Bullion Depository at Fort Knox.
Since 1968 the price of gold on the open market has ranged widely,
with a record high of $850/oz ($27,300/kg) on 21 January 1980, to
a low of $252.90/oz ($8,131/kg) on 21 June 1999 (London Fixing). On
11 May 2006 the London gold fixing was $715.50/oz ($23,006/kg).
In 2005 the World Gold Council estimated total global gold supply
to be 3,859 tonnes and demand to be 3,754 tonnes, giving a surplus
of 105 tonnes.
Compounds
Although gold is a noble metal, it forms many and diverse compounds.
The oxidation state of gold in its compound ranges from -1 to 5+ but
Au(I) and Au(III) dominate. Gold(I), referred to as the aurous ion,
is the most common oxidation state with "soft" ligands such
as thioethers, thiolate]]s, and tertiary phosphine]]s. Au(I) compounds
are typically linear. A good example is Au(CN)2-, which is the soluble
form of gold encountered in mining. Curiously, aurous complexes of
water are rare. The binary gold halides, such as AuCl, form zig-zag
polymeric chains, again featuring linear coordination at Au. Most
drugs based on gold are Au(I) derivatives.
Gold(III) ("auric") is a common oxidation state and is illustrated
by gold(III) chloride, AuCl3. Its derivative is chloroauric acid,
HAuCl4, which forms when Au dissolves in aqua regia. Au(III) complexes,
like other d8 compounds, are typically square planar.
Less common oxidation states: Au(-I), Au(II), and Au(V)
Compounds containing the Au- anion are called aurides. Caesium auride,
CsAu which crystallizes in the caesium chloride motif. Other aurides
include those of Rb+, K+, and tetramethylammonium (CH3)4N+. Gold(II)
compounds are usually diamagnetic with Au-Au bonds such as [Au(CH2)2P(C6H5)2]2Cl2.
A noteworthy, legitimate Au(II) complex contains xenon as a ligand,
[AuXe4](Sb2F11)2. Gold pentafluoride is the sole example of Au(V),
the highest verified oxidation state.
Some gold compounds exhibit aurophilic bonding, which describes the
tendency of gold ions to interact at distances that are too long to
be a conventional Au-Au bond but shorter that van der Waals bonding.
The interaction is estimated to be comparable in strength to that
of a hydrogen bond.
Mixed valence compounds
Well-defined cluster compounds are numerous. In such cases, gold has
a fractional oxidation state. A representative example is the octahedral
species {Au(P(C6H5)3)}62+. Gold chalcogenides, e.g. "AuS"
feature equal amounts of Au(I) and Au(III).
Isotopes
There is one stable isotope of gold, and 18 radioisotopes with Au
being the most stable with a half-life of 186 days.
Gold has been proposed as a "salting" material for nuclear
weapons (cobalt is another, better-known salting material). A jacket
of natural gold, irradiated by the intense high-energy neutron flux
from an exploding thermonuclear weapon, would transmute into the radioactive
isotope Au-198 with a half-life of 2.697 days and produce approximately
.411 MeV of gamma radiation, significantly increasing the radioactivity
of the weapon's fallout for several days. Such a weapon is not known
to have ever been built, tested, or used.
Gold has been associated with the extremities of utmost evil and great
sanctity throughout history. In the Book of Exodus, the Golden Calf
is a symbol of idolatry and rebellion against God. In Communist propaganda,
the golden pocket watch and its fastening golden chain were the characteristic
accessories of the class enemy, the bourgeois and the industrial tycoons.
Credit card companies associate their product with wealth by naming
and colouring their top-of-the-range cards "gold;" although,
in an attempt to out-do each other, platinum (and the even-more-elite
black card) has now overtaken gold.
On the other hand in the Book of Genesis, Abraham was said to be rich
in gold and silver, and Moses was instructed to cover the Mercy Seat
of the Ark of the Covenant with pure gold. Eminent orators such as
John Chrysostom were said to have a "mouth of gold with a silver
tongue." Gold is associated with notable anniversaries, particularly
in a 50-year cycle, such as a golden wedding anniversary, golden jubilee,
etc.
Great human achievements are frequently rewarded with gold, in the
form of medals and decorations. Winners of races and prizes are usually
awarded the gold medal (such as the Olympic Games and the Nobel Prize),
while many award statues are depicted in gold (such as the Academy
Awards, the Golden Globe Awards the Emmy Awards, the Palme d'Or, and
the British Academy Film Awards).
Medieval kings were inaugurated under the signs of sacred oil and
a golden crown, the latter symbolizing the eternal shining light of
heaven and thus a Christian king's divinely inspired authority. Wedding
rings are traditionally made of gold; since it is long-lasting and
unaffected by the passage of time, it is considered a suitable material
for everyday wear as well as a metaphor for the relationship. In Orthodox
Christianity, the wedded couple is adorned with a golden crown during
the ceremony, an amalgamation of symbolic rites.
The symbolic value of gold varies greatly around the world, even within
geographic regions. For example, gold is quite common in Turkey but
considered a most valuable gift in Sicily.
From most ancient times, gold has been connected to religion and spirituality,
especially associated with the Sun. It was also seen as the best material
to decorate religious imagery, all over history.
A gold certificate in general is a certificate of ownership that gold
owners hold instead of storing the actual gold. It has both a historic
meaning as a US paper currency (1882-1933) and a current meaning as
a way to invest in gold.
A Gold Sovereign is a gold coin first issued in 1489 for Henry VII
of England and still in production as of 2007 [1]. The coin generally
had a value of one pound sterling. The name "sovereign"
comes from the majestic and impressive size and portraiture of the
coin, the earliest of which showed the king facing, seated on a throne,
while the reverse shows the Royal coat of arms on a shield surrounded
by a Tudor double rose. These original sovereigns were 23 carat (96%)
gold and weighed 240 grains or one-half of a troy ounce (15.6 grams).
Henry VIII reduced the purity to 22 carats (92%), which eventually
became the standard; the weight of the sovereign was repeatedly lowered
until when it was revived after the Great Recoinage law of 1816, the
gold content was fixed at the present 113 grains (7.32 g), equivalent
to 0.2354 Troy ounces
Sovereigns were discontinued after 1604, being replaced by Unites,
and later by Laurels, and then guineas. Production of sovereigns restarted
in 1817, their reverse design being a portrayal of Saint George killing
a dragon, engraved by Benedetto Pistrucci. This same design is still
in use on British gold sovereigns, although other reverse designs
have also been used during the reigns of William IV, Victoria, George
IV, and Elizabeth II.
In Victorian times it was the practice of the Bank of England to remove
worn sovereigns and half sovereigns from circulation and have them
recoined. Consequently, although a billion sovereigns have been minted
in total, that figure includes gold that has been coined and recoined
a number of times. It is estimated that in circulation, a sovereign
could have a lifespan of up to 14 years before it fell below the "least
current weight", that is, the minimum amount of gold below which
it ceased to be legal tender. It was actually the half-sovereign that
had the most circulation in Victorian England. Many sovereigns languished
in bank vaults for most of their lives. It is estimated that only
1% of all gold sovereigns that have ever been minted are still in
collectible condition.
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