Gold Essay, Research Paper

Antwan Lucas

Gold

Gold, symbol Au , 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.

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 black; colloidally 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 2808. C

(about 5086. F), and has a specific gravity of 19.3; its

atomic weight is 196.97.

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 75th 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.

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 composed of 90 parts

gold to 10 parts silver. Green gold used in jewelry

contains copper and silver; white gold contains zinc and

nickel, or platinum metals.

Gold is also used in the form of gold leaf in the arts

of gilding and lettering. Purple of Cassius, a

precipitate of finely divided gold and stannic hydroxide

formed by the interaction of auric chloride and stannous

chloride, is used in coloring ruby glass. Chlorauric

acid is used in photography for toning silver images.

Potassium gold cyanide is used in electrogilding. Gold

is also used in dentistry. Radioisotopes of gold are

used in biological research and in the treatment of

cancer (see Isotopic Tracer).

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, 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.

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 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,

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 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 Qu bec. 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 474 metric tons in 1998; 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 1998, the amount of gold produced in the United

States was 366 metric tons. U.S. consumption, by major

markets, included jewelry and arts, 55 percent;

industry, 42 percent; 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.

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