DEFINITION OF GOLD

A soft, yellow, native metallic element widely used for

jewelry, ornaments, and as the international standard for

world finance. Along with silver and copper, gold has been

sought after by our human ancestors for seven or eight thousand

years as a valuable and malleable decorative metal; since

it was found in its native form, it is highly malleable and has

desirable aesthetic properties.

Gold usually occurs as a native metal in deposits and typically

has some silver mixed with it by atomic substitution.

Deposits may be lode or placer type, with lode gold including

primary deposits in hard rock (typically metamorphic or

igneous), and placer deposits being secondary, found in stream

gravels or soils. Lode gold deposits are formed by hot aqueous

solutions that move through the crust and are typically associated

with the marginal zone or aureoles of plutons. Other

lode gold deposits seem to be associated with regional metamorphic

fluids, or meteoric waters that circulate deeply and

get heated, deposit gold where they cool or react chemically

with wall rocks of different composition. Many of the world’s

famous gold mines are associated with quartz-pyrite-gold

veins in faults, including the Mother Lode in California, the

Bendigo and Ballarat lodes of Australia, and the ancient

workings of the Pharos in the Southeastern Desert of Egypt.

Lode gold deposits that form under low pressures and low to

intermediate temperatures (302°F–662°F, or 150°C–350°C)

are classified as epithermal deposits and tend to be associated

with convergent margins.

Gold is chemically unreactive, so it persists through

weathering and transportation, and gets concentrated in soils

and as heavy minerals in stream placer deposits. Placer gold

was the sought-after treasure in the great gold rushes of the

Fairbanks gold district and Yukon territories of Canada,

where placer and lode deposits are still being discovered and

mined. One of the biggest ancient placer deposits in the

world is in the 2.6–2.7-billion-year-old Witwatersrand basin

of southern Africa, which has supplied more than 40 percent

of the gold ever mined in the world.

Title Post:
Rating: 100% based on 99998 ratings. 99 user reviews.
Author:

Terimakasih sudah berkunjung di blog SELAPUTS, Jika ada kritik dan saran silahkan tinggalkan komentar