Gold

Gold

What is Gold: 

Gold is a yellow to a pale whitish-yellow metal with the formula Au. It has a metallic luster, a hardness of 2.5 to 3, and an atomic number of 79 on the periodic table. 

The majority of gold produced nowadays is used in the production of jewelry. However, gold emerged as an essential industrial metal in the late twentieth century because of its better electrical conductivity and corrosion resistance.

Gold serves vital tasks in computers, communications equipment, spacecraft, jet aircraft engines, and various other items. Although gold is essential in industry and the arts, it also has a unique position among commodities as a long-term store of wealth.

Gold primarily occurs in three types of deposits: 

  1. Hydrothermal quartz veins and associated deposits in metamorphic and igneous rocks
  2. Volcanic-exhalative sulfide deposits
  3. Placer deposits - a type of mineral deposit in which grains of a valuable mineral like gold or the rare earth is mixed with sand deposited by a river, stream, or glacier.
In hydrothermal deposits, gold is dispersed along the quartz veins with pyrite and other accessory minerals. In placer deposits, gold can occur as rounded grains and flakes or nuggets in placer deposits. Nuggets are almost exclusively hypogene in origin, mainly forming in veins, but can be somewhat modified in form and chemistry by weathering, erosion, and transport (Hough et al., 2007).

 

History: 

Since prehistoric times, gold has been known and was one of the earliest metals to be mined, owing to its availability as nuggets or particles in stream beds. The first known gold mining operations dating back to 2000 BC in Egypt. The death mask of Tutankhamen, who died in 1323 BC, contained 100 kg of gold. The royal graves of ancient Ur, which is modern Iraq, also had gold. Iraq and many middle eastern countries still have gold. Given how valuable gold is commercially for use in technology, it's rumored that many modern wars in the middle east were for critical minerals such as gold rather than protecting the people. 

 

Until recently, it was primarily regarded as a monetary metal, with the majority of bullion produced each year ending up in the vaults of government treasuries or central banks. Minting gold coins began around 640 BC in the Kingdom of Lydia (situated in what is now modern Turkey) using electrum, a native alloy of gold and silver. However, the first pure gold coins were minted in the reign of King Croesus, who ruled from 561–547 BC.

 

Luster: Metallic

Transparency: Opaque

Color: Rich yellow, paling to whitish-yellow with increasing silver; blue & green in transmitted light (only thinnest folia [gold leaf])

Streak: Shining yellow

Hardness: 2.5 - 3

Hardness: VHN10=30 - 34 kg/mm2 - Vickers

Hardness Data: Measured

Tenacity: Malleable

Cleavage: None Observed

Fracture: Hackly

Density: 15 - 19.3 g/cm3 (Measured) 19.309 g/cm3 (Calculated)

 

 

Mineral Commodity Profiles—Gold By W.C. Butterman and Earle B. Amey III

 

 

 

 

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