Photo of Gold in Processed & Rough Form
Gold is a mineral with a hardness of 2 out of 10 on the Mohs scale of mineral hardness [?]. These Cubicly structured gems are made of gold, their full chemical compound being Au.
Gold is a Native Element that appears in very rare, small, octahedral, cubic, and dodecahedral crystals. It normally occurs in very small, shapeless grains, sheets, and flakes. Dendrites are rare. Nuggets are common in alluvial or glacial deposits.
It is of yellow color, varying in brightness, depending on the impurities present. This bright, rich yellow is resistant to tarnishing. Gold is often rich in silver, when it is paler in color.
It is fairly soft, very heavy, ductile, and malleable, and is opaque, with bright metallic luster. Very thin sheets let through feeble, greenish light.
Gold's insolubility in acids (except aqua regia-nitro hydrochloric acid), and its specific gravity distinguish it from yellow sulfides and from the small altered plates of biotite often found in sands, where it is associated with pyrite and arsenopyrite. It also occurs in various volcanic rocks and tuffs, associated with chalcedony and manganese minerals. Large concentrations known as bonanzas are formed by the erosion and redeposition of gold-bearing lavas.
It occurs primarily in high-temperature hydrothermal quartz veins in extrusive rocks. It is frequently found as a natural alloy with silver (electrum), and less often with palladium (porpezite) and rhodium (rhodite).
Most gold is obtained from concentrations of sedimentary origin (placers), both recent (river sand) and fossil deposits (conglomerate matrix), where it is accompanied by other heavy minerals. Panning for gold by sifting the sediment is an age-old method of looking for this rare and valuable mineral. Gold flakes are also found in the cementation zones of sulfide, selenide, and telluride deposits, formed at high temperature under hydrothermal conditions.
The main gold-bearing districts are the Witwatersrand (South Africa), the Mother Lode (California, USA), the Yukon (Alaska, USA), Porcupine (Northwest Territory, Canada), and the Soviet Republics.
Gold can be confused with pyrite and chalcopyrite which are harder and more brittle. But only a few tests are needed to identify it.
Gold Resources
- Gold Value-Nice gold calculator that calculates value of gold in various karats and weights.
- Gold Price Per OZ-Site that lists live gold prices per ounce, as well as the melt values for most gold coins. Live value updated every few minutes it looks like.
- Gold (Wiki)-Gold article from Wikipedia goes into a little more detail in regards to this yellow metal.
The specific gravity [?] for Gold is 19.3, its refractive index [?] is None, and its double refraction [?] is None.
History
Most of the Earth's gold lies at its core, because its high density made it sink there in the planet's youth.
Gold artifacts have been from the Chalcolithic period. Artifacts in the Balkans also appear from 4000 BC. Egyptian hieroglyphs from as early as 2600 BC describe gold, was "more plentiful than dirt." The earliest known map is known as the Turin Papyrus Map and shows the plan of a gold mine in Nubia. Large mines were also present across the Red Sea in what is now Saudi Arabia.
The old symbol for gold was a circle, a reflection of its ancient identity with the sun.
The European exploration of the Americas was fueled by reports of the gold ornaments displayed as common by Native American peoples. The Aztecs regarded gold as literally the product of the gods, calling it "god excrement." For the indigenous peoples of North America, gold was considered useless, as they considered minerals like obsidian, flint, and slate to be more valuable according to their use.
The largest gold nugget recorded was 214 kg (472lbs). It was found in 1872 at Holterman's Reef, New South Wales (Australia).
Industrial Usages
Gold has a medium fusion point 1061°C/1942°F. It is an excellent conductor of heat and electricity.
It is used mainly as a monetary standard, in jewelry, in dentistry, and for scientific and electronic instruments.
Pure metallic gold is too soft for use in jewelry or coin, but as an alloy with copper, palladium, silver, or other metals, depending on the hardness and the desired color and intended use.
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