Gold

Short Course Project

1. GOLD
Presented to,
Sir Inam ul Haq
Submitted by,
Syeda Mehvish Dildar
University of Education
Lahore

2. ProjectProject
Jauharabad campus
July 12, 2007

1.INTRODUCTION
Gold, symbol Au (from Latin aurum, “gold”), soft, dense,
bright yellow metallic element. Gold is one of the transition
elements of the periodic table (see Periodic Law); its atomic
number is 79.
2.PROPERTIES
Pure gold is the most malleable and ductile of all the
metals. It can easily be beaten or hammered to a thickness
of 0.000013 cm (0.000005 in), and 29 g (1.02 oz) could be
drawn into a wire 100 km (62 mi) long. It is one of the
softest metals (hardness, 2.5 to 3) and is a good conductor
of heat and electricity. Gold is bright yellow and has a high
luster. Finely divided gold, like other metallic powders, is
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black; colloid ally suspended gold ranges in color from ruby
red to purple (see Colloid).
Gold is extremely inactive. It is unaffected by air, heat,
moisture, and most solvents. It will, however, dissolve in
aqueous mixtures containing various halogens such as
chlorides, bromides, or some iodides. It will also dissolve in
some oxidizing mixtures, such as cyanide ion with oxygen,
and in aqua regia, a mixture of hydrochloric and nitric acids.
The chlorides and cyanides are important compounds of
gold. Gold melts at about 1064°C (about 1947°F), boils at
about 2856°C (about 5173°F), and has a specific gravity of
19.3; its atomic weight is 196.97.
3.OCCURRENC
E
Gold is found in nature in quartz veins and secondary
alluvial deposits as a free metal or in a combined state. It is
widely distributed although it is rare, being 75
th
in order of
abundance of the elements in the crust of the Earth. It is
almost always associated with varying amounts of silver;
the naturally occurring gold-silver alloy is called electrum.
Gold occurs, in chemical combination with tellurium, in the
minerals calaverite and sylvanite along with silver, and in
the mineral nagyagite along with lead, antimony, and sulfur.
It
Occurs with mercury as gold amalgam. It is generally
present to a small extent in iron pyrites; galena, the lead
sulfide ore that usually contains silver, sometimes also
contains appreciable amounts of gold. Gold also occurs in
seawater to the extent of 5 to 250 parts by weight to 100
million parts of water. Although the quantity of gold present
in seawater is more than 9 billion metric tons, the cost of
recovering the gold would be far greater than the value of
the gold that could thus be recovered.
4.USE
S
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The metal has been known and highly valued from earliest
times, not only because of its beauty and resistance to
corrosion, but also because gold is easier to work than all
other metals. In addition, gold was easier to obtain in pure
form than the other metals. Because of its relative rarity,
gold became used as currency and as a basis for
international monetary transactions (see Dollar; Gold
Standard). The unit used in weighing gold is the troy ounce;
1 troy ounce is equivalent to 31.1 grams.
The major portion of the gold produced is used in coinage
and jewelry (see Metalwork). For these purposes it is
alloyed with other metals to give it the necessary hardness.
The gold content in alloys is expressed in carats (see
Carat). Coinage gold is alloyed with copper or silver. Green
gold used in jewelry contains copper and silver; white gold
contains zinc and nickel, or platinum metals.
GoldGold isis alsoalso usedused ii
nn the form of gold the form of gold
leaf in the arts of leaf in the arts of
gilding and gilding and
lettering. Purple oflettering. Purple of
Cassius, a Cassius, a
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precipitate of precipitate of
finely divided goldfinely divided gold
and stannic and stannic
hydroxide formed hydroxide formed
by the interaction by the interaction
of auric chloride of auric chloride
and stannous and stannous
chloride, is used chloride, is used
in coloring ruby in coloring ruby
glass. Chlorauric glass. Chlorauric
acid is used in acid is used in
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photography for photography for
toning silver toning silver
images. images.
Potassium gold Potassium gold
cyanide is used in cyanide is used in
electro gildingelectro gilding. .
Gold is also used Gold is also used
in dentistry. in dentistry.
Radioisotopes of Radioisotopes of
gold are used in gold are used in
biological biological
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research and in research and in
the treatment of the treatment of
cancer (see cancer (see
Isotopic Tracer).Isotopic Tracer).
5.GOLD
MINING
The simplest process used for mining gold is panning, using
a circular dish often with a small pocket at the bottom. The
prospector fills the dish with gold-bearing sand or gravel,
holds it under a gentle stream of water, and swirls it. The
lighter parts of the gravel are gradually washed off and the
gold particles are left near the center of the pan or in the
pocket.
As gold mining developed, more elaborate methods were
introduced and hydraulic mining was invented. The hydraulic
method consists of directing a powerful stream of water
against the gold-bearing gravel or sand. This operation
breaks down the material and washes it away through
specially constructed sluices in which the gold settles, while
the lighter gravel is floated off. For mining on rivers,
elevator dredges are generally used. The elevator dredge is
a flat-bottomed boat that uses an endless chain of small
buckets to scoop up the material from the river bottom and
empty it on the dredge into a trommel (a container built of
screening). The material is rotated in the trommel as water
is played on it. The gold-bearing sand sinks through
perforations in the trommel and drops onto shaking tables,
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on which it is further concentrated. Dredging can also be
used in dry beds of ancient rivers if ample water is within a
reasonable distance. A pit is dug, and the dredge is moved
in and floated on water pumped from the adjacent source.
Extensive underground deposits of gold-bearing rocks are
often discovered by a small outcrop on the surface. Shafts
are sunk, as in coal mining, and the ore is brought to the
surface. It is then crushed in special machines.
Gold is extracted from gravel or from crushed rock by
dissolving it either in mercury (the amalgam process) or in
cyanide solutions (the cyanide process). Some ores,
especially those in which the gold is chemically combined
with tellurium, must be roasted before extraction. The gold
is recovered from the solution and melted into ingots. Gold-
bearing rock with as little as 1 part of gold to 300,000 parts
of worthless material can be worked at a profit.
The rarest form of gold is a nugget. The largest known
nugget, the Welcome Stranger, weighing 2,284 troy oz
(equivalent to 59.0 kg/130.1 pounds), was turned up
accidentally, just below the surface of the ground, by a
wagon wheel in Victoria, Australia, in 1869.
6.GOLD
PRODUCTION
Gold production dates from the Etruscan, Minoan, Assyrian,
and Egyptian civilizations, when placer gold was derived
from alluvial sands and gravels by simple processes of
washing or panning. Gold was produced in this manner at an
early period in India, central Asia, the southern Ural
Mountains and in the regions bordering the eastern
Mediterranean. With progress in mining technique, primary
auriferous (gold-bearing) veins were exploited; this type of
gold mining attained some importance before the Christian
era. During the middle Ages little progress was made in gold
production and mining.
At the time of the discovery of the Americas the value of the
total gold stock of Europe was probably less than $225
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million. During the succeeding 350 years, from the end of
the 15th century to about 1850, the world gold output
totaled about 4,665,000 kg (about 150 million troy oz).
South America and Mexico became large producers of gold
during this period. Spain's domination in South America
resulted, in the 16th century, in a large increase in gold
produced in the New World; some resulted from simple
seizure of gold from the Native Americans, who had long
mined the metal. In the same century Mexico contributed
about 9 percent of the total world production. Gold was
discovered in Australia in February 1851, and rich fields
were found there.
By the middle of the 19th century the United States
produced a considerable percentage of the world gold
production. In the United States gold has been produced in
two regions: the eastern region along the Appalachian
Mountains, and the western region along the Rocky
Mountains and the Sierra Nevada, Coast, and Cascade
ranges. Gold has been found in numerous places on the
eastern slope of the Appalachians from Newfoundland and
Labrador, Canada, to Alabama, although workable deposits
occur only in Nova Scotia and in the southern United States.
In the South the auriferous belt, ranging up to 120 km (75
mi) in width, extends from Virginia through North Carolina,
South Carolina, and Georgia into Alabama. Both veins and
surface deposits have been worked; some pockets of ore
were exceptionally rich. The first gold shipped to the United
States Mint for coinage from the southern states was from
North Carolina in 1804. For the next 20 years the value of
the annual output of North Carolina amounted to less than
$2,500. In 1829 Virginia and South Carolina, in 1830
Georgia, in 1831 Alabama and Tennessee, and in 1868
Maryland shipped gold to the mint for coinage.
The western gold fields extend in the Cordilleran region
from Alaska to Mexico. Gold was discovered first in this
region in California on January 24, 1848, during excavation
for a sawmill on land settled by the American pioneer John
Sutter. During the next five years gold valued at more than
$285 million, an amount 21 times greater than the value of
the total previous production of the entire country, was
produced in California. The gold rush took place at this
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time, when people from all parts of the world rushed to the
new gold district (see Forty-niners). The discovery furnished
the incentive for the exploration and development of the
whole far-western section of the United States. The
Comstock Lode, a famous discovery made in 1859, is
situated on an eastern spur of the Sierras, extending into
Nevada. Placers and veins similar to those of the Sierras are
found also in Oregon and Washington. The Rocky Mountains
and the outlying ranges, which were first prospected in the
early 1860s, include an immense area of gold-bearing
territory. Rich gravels have been worked at the following
locales: near Leadville, Fairplay, and in San Miguel County,
Colorado; near Helena and Butte, Montana; along the Snake
and Salmon rivers, Idaho; near Deadwood, South Dakota; at
Santa Fe, New Mexico; and in Alaska.
Placer deposits of gold were discovered on the Yukon River
in Canada and Alaska in 1869. The discovery in 1896 of a
rich deposit in the Bonanza Creek, a headwater of the
Klondike River, which in turn is a tributary of the Yukon, led
to another gold rush. In 1910 discoveries were made on
Bitter Creek, near Stewart, British Columbia. In 1911 gold
was also discovered in Alaska, some 30 km (some 20 mi)
from the Canadian boundary at the source of the Sixty Mile
River, which rises in Alaska and flows into the Yukon River.
Since 1911 the production of gold in Ontario, in the
Porcupine and Kirkland lake districts, has gone ahead
rapidly. Important discoveries of gold mixed with copper
were made in northwestern Québec. The gold production of
Australia has been famous since 1851; the chief centers of
production are in Western Australia and Victoria.
South Africa is the world's leading supplier of gold,
producing 376 metric tons in 2003; its most important gold
mines are in the Witwatersrand region. Some 70 other
countries produce gold in commercial quantities, but two
thirds of the total worldwide production now comes from
South Africa, the United States, Australia, China, Canada,
and Russia.
In 2003, the amount of gold produced in the United States
was 277 metric tons. U.S. consumption, by major markets,
included jewelry and arts, 55 percent; industry, 42 percent;
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and dental, 3 percent. Most jewelry manufacturing in the
United States is centered in New York City and Providence,
Rhode Island.
On December 31, 1974, the U.S. federal government lifted a
41-year ban on the private ownership of gold. Around that
time gold was being traded on the London bullion market at
record highs approaching $200 an ounce. After subsequent
sharp decreases, prices rose to a high of $850 in January
1980. They then dropped considerably and in the early
1990s settled at about $370 an ounce.
Summary
(Gold)
Gold, symbol Au (from Latin aurum,
“gold”), soft, dense, bright yellow metallic
element. Gold is one of the transition
elements of the periodic table (see Periodic
Law); its atomic number is 79.
Gold is found in nature in quartz veins and
secondary alluvial deposits as a free metal
or in a combined state. It is widely
distributed although it is rare, being 75
t h
in order of
abundance of the elements in the crust of the Earth.
Pure gold is most malleable and ductile of all the metals. It
can easily be beaten or hammered to a thickness of 0.000013
cm (0.000005 in), and 29 g (1.02oz) could be drawn into a
wire 100 km (62mi) long. It is one of the softest metals
(hardness, 2.5 to 3) and is a good conductor of heat and
electricity.
Gold is bright yellow and has a high luster. Finely Divided
gold, like other metallic powders, is black; colloid ally
suspended gold ranges in color from ruby red to purple (see
colloid).
The metal has been known and highly valued from earliest
times, not only because of its beauty and resistance to
corrosion, but also because gold is easier to work than all
other metals. In addition, gold was easier to obtain in pure
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form than the other metals. Because of its relative rarity,
gold became used as currency and as a basis for
international monetary transactions (see Dollar; Gold
Standard). The unit used in weighing gold is the
troy ounce; 1 troy ounce is equivalent to 31.1 grams. In
fact, gold is very use full metal.
July7,2007

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