Gold

Gold is shiny. Gold is glamorous. Gold does not corrode. So it became a symbol of immortality, wealth and power in many ancient cultures. Due to is preciousness Gold has always been used for coinage, jewellery and ornaments. Today thanks to its specific characteristic this noble metal is also used in Medicine, Computers, Electronics.

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What is Gold?

Gold is a member of the transition metals and sits in the same periodic table column as silver and copper. The group that gold can be found in is often termed the ‘coinage metal‘ group since its members are frequently used to produce money. Gold is, in fact, one of the first metals known to man with its origin being dated back to 3400 BCE by the Egyptians. Gold has always been a symbol of wealth and beauty. During Egypt’s reign of Pharaoh’s, the Egyptians would often amass tremendous amounts of gold just to cover the coffin of a deceased Pharaoh.
Interestingly enough, when King Tutankhamun, commonly referred to as King Tut, died, his coffin contained approximately 112 kg of gold.


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Funeral gold mask of tutankhamon

Trace amounts of gold are found almost everywhere, but large deposits are found in only a few locations. Although there are about twenty different gold minerals, all of them are quite rare. Therefore, most gold found in nature is in the form of the native metal.

Gold occurs in hydrothermal veins deposited by ascending solutions, as disseminated particles through some sulfide deposits, and in placer deposits.

Info source: http://study.com/academy/lesson/what-is-gold-definition-properties-uses.html

http://geology.com/minerals/gold.shtml

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How does Gold form?

On Earth, gold reached us some 200 million years after the formation of the planet when meteorites packed with gold and other metals bombarded its surface. During the formation of Earth, molten iron sank to its centre to make the core.

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gold formation

Another theory concerning the formation of gold that’s been gaining a lot of traction today is that the element can form following the collision of two neutron stars. Following the collapse of a massive star what remains is a extremely dense core.

Two neutron stars in mutual orbit can collide when gravitational waves carry enough energy away from the system to destabilize the orbit. When this happens, a type of gamma-ray burst can occur – these are the most powerful explosions in the universe. The intense energy would be enough to create gold and other heavy elements, according to a paper published in the Astrophysical Journal Letters.

Info source: http://www.zmescience.com/science/how-gold-is-made-science-064654/

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What are the types of Gold?

  • Yellow-gold-color: yellow-gold-colorYellow gold is made by mixing pure gold with silver, copper, and zinc. It is the purest color, the most hypo-allergenic, and requires the least maintenance of all the gold colors.
  • White-gold-color: white-gold-colorWhite gold is made of gold and platinum (or palladium). White gold can also be made of gold, palladium, nickel and zinc. White gold is more durable and scratch-resistant than yellow gold. It is also more affordable than both yellow gold and platinum.
  • Rose-gold-color: rose-gold-colorRose gold (or pink gold) is alloyed with gold, copper, and silver. Rose gold is more affordable than the other gold colors because it uses the inexpensive copper for its rose color. Due to its copper content, rose gold is more durable than yellow or white gold.
  • Green-gold-color: green-gold-colorGreen gold (or Electrum) is mixed with gold, silver, and sometimes copper. Silver is what gives the gold alloy the green nuance.

 

Info and image source: http://www.peridot.com/types-of-gold/

What are the stages of Gold working?

Gold is usually found in a pure state; however, it can also be extracted from silver, copper, lead and zinc.

  • Mining
  1. In lode or vein deposits, the gold is mixed with another mineral, often quartz. Gold is obtained from lode deposits by drilling, blasting, or shoveling the surrounding rock.
    Lode deposits often run deep underground. The gold ore is then gathered up and taken to a mill for refinement.
  2. Placer deposits contain large pieces of gold ore (nuggets) and grains of gold that have been washed downstream from a lode deposit and that are usually mixed with sand or gravel. The three main methods used to mine placer deposits are hydraulic mining, dredging, and power shoveling. All methods of placer deposit mining use gravity as the basic sorting force.
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gold mining
  • Grinding
    Once the gold ore has been mined, it usually is washed and filtered at the mine as a preliminary refinement technique. It is then shipped to mills, where it is first combined with water and ground into smaller chunks. The resulting mixture is then further ground in a ball mill.
  • Separating the gold from the ore
  1. The gold is then separated from the ore using one of several methods. Floatation involves the separation of gold from its ore by using certain chemicals and air.
  2. Cyanidation also involves using chemicals to separate the gold from its contaminants.
  3. The carbon-in-pulp method also uses cyanide, but utilizes carbon instead of zinc to precipitate the gold.
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gold smelting
  • If the gold is still not pure enough, it can be smelted. Smelting involves heating the gold with a chemical substance called flux. The flux bonds with the contaminants and floats on top of the melted gold. The gold is then cooled and allowed to harden in molds, and the flux-contaminant mixture (slag) is hauled away as a solid waste.

Info source: http://www.madehow.com/Volume-1/Gold.html

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http://www.cnbc.com/2013/12/23/mexicos-economy-may-surprise-you.html

What are Gold characteristics?

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Golden sheets

Gold is a soft, yellow metal. Like all other metals, gold is also highly malleable and ductile. Moreover, gold is able to conduct both electricity and heat rather easily. Gold has an extremely high density at 19.3 g per cubic centimeter, slightly greater than lead. Like all other metals, gold is malleable. However, it’s much more easily pressed-out than most other metals. In fact, just one ounce of gold can be stretched to over 300 square feet. Some other properties of gold include its high resistance to oxidation. Typically, metals often form oxide later on their surface due to exposure to oxygen at room tmpetarure and room conditions;gold doesn’t form this layer easily. additionally, gols is unaffected by most acids and bases. Gold is quite resilient.

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How was Gold used throughout history?

Gold, chemical symbol Au (from the Latin aurum meaning ‘shining dawn’), is a precious metal which has been used since antiquity in the production of jewellery, coinage, sculpture, vessels and as a decoration for buildings, monuments and statues.

Macedonian Gold Stater
Ancient gold coins

Gold does not corrode and so it became a symbol of immortality and power in many ancient cultures. Its rarity and aesthetic qualities made it an ideal material for ruling classes to demonstrate their power and position. First found at surface level near rivers in Asia Minor such as the Pactolus in Lydia, gold was also mined underground from 2000 BCE by the Egyptians and later by the Romans in Africa, Portugal and Spain. There is also evidence that the Romans smelted gold particles from ores such as iron pyrites. Easily worked and mixed with other metals such as silver and copper to increase its strength and change its colour, gold was used for a wide range of purposes.

Info and image source: http://www.ancient.eu/gold/

Where can we find Gold today?

Gold is chiefly used for:

  • Coinage
  • Ornaments
  • Jewellery
  • Gilding

Other uses for gold include:

  • Textile industry
  • Gold flake is used for a radiation-control coating for spacecraft
  • In electronic tubes, as gold-plated grid wire, to give high conductivity and suppressing secondary emissions
  • Gold powder and gold sheet is used for soldering semiconductors, with gold having a good ability to wet silicon at 371°C (725°F)
  • Gold is used as a plating material, where sodium gold cyanide [NaAu(CN)2] is used as a gold plating solution. The plating has good chemical resistance and electrical properties, however the plating lacks wear resistance, in which case gold-indium plate is utilised.
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gold wire

Gold alloys also have a number of applications such as:

 

  • Gold-gallium and gold-antimony are used in electronic industry (primarily as wire)
  • Gold is used for dental applications and is rightly termed dental gold, where gold is alloyed with silver, platinum and on occasion palladium. It is sometimes alloyed with iridium for hardening.

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    Johnny Depp with the golden teeth

Info source: http://www.azom.com/article.aspx?ArticleID=598

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