Materials Mondays; The Dragons Precious..... GOLD!

Posted by Stephenie Denault on

No dragons den is complete without its precious gold! But what makes it so precious?

Golden Standards

Gold is a chemical element. In a pure form, its bright, slightly reddish yellow, dense, soft, malleable and ductile. It often occurs in free elemental form as nuggets or grains, in rocks.

It's resistant to most acids and is a relatively rare element. It's a precious metal that has been used for coinage, jewellery, and other arts.

A "Gold Standard" was often implemented as a monetary policy, but in the 1930's gold coins stopped being minted as a circulating currency and the world gold standard was abandoned for a flat currency system after 1971. 

Fun Fact!

As of 2019, 197,576 tonnes of gold exists above ground! 

Imagine a huge cube measuring 21.7 meters on each side!!!! That is a LOT of gold!
The current world consumption of new gold produced is about 50% jewellery, 40% investments and 10% industry. 

History and Culture

The earliest recorded metal employed by humans, appears to be gold. Small amounts of natural gold have been found in Spanish caves used during the late Paleolithic Period c. 40,000 BC.
Artifacts made from gold appeared at the beginning of the predynastic period in Egypt, at the end of the fifth millennium BC and the start of the fourth

Culturally, gold is mentioned in a variety of expressions most often associated with intrinsic worth.
Great human achievements are frequently rewarded with gold. Gold medals, trophies and other decorations. Winners of athletic events and other graded competitions are usually awarded a gold medal. Even the Nobel Prize is made from gold!

Aristotle in his ethics used gold symbolism referring to what's now known as the "Golden Means". Similarly, gold is associated with perfect or divine principles. "Golden Rule" or "Golden Ratio". It's associated with the wisdom of aging, The 50th wedding anniversary is "Golden". 
A person's most successful latter years are sometimes considered as their "Golden Years" and the height of a civilization is referred to as the "Golden Age"

Karats

A karat is a measurement of the fineness of a piece of gold. The fineness represents the weight of fine metal it contains in proportion to the total weight including alloyed metals & impurities. 

With gold, a karat is a fractional measure of purity for gold alloys, measured 24 parts per whole.
Pure gold that hasn't been mixed with other metals is therefore the highest possible karat, 24 karat (24K) gold.
Though more valuable, pure gold is rarely used for jewellery because of its softness and malleability, therefore its usually alloyed with base metals altering its malleability, colour & properties.
Gold is often mixed with silver, zinc, copper or palladium creating a different number of karats and colours like rose gold or white gold.
Traditional karats used in jewellery number from pure gold at 24k, 22k,18k,14k,or 10k. 

Here is a Gold conversion chart for reference!

Number of Karats Fraction of Gold % of Gold Purity Millesimal fineness
9K 9/24 37.5 375
10K 10/24 41.7 416/417
12K 12/24 50.0 500
14K 14/24 58.3 583/585
18K 18/24 75.0 750
22K 22/24 91.7 916/917
24K 24/24 99.9 999

 

"All that is gold does not glitter " ~J.R.R Tolkien~

Gold groups and colours

Pure Gold is slightly reddish in colour, but coloured gold in various other colours can be produced. 

Coloured golds can be classified into three groups:

1. Alloys with silver and copper in various proportions, producing white, yellow, green and red golds. These are usually malleable alloys.

Examples of colours and their respective alloys:

  • White Gold: alloy of gold and one white metal (nickel, silver or palladium)
  • Yellow Gold: alloy of gold, copper and silver
  • Rose, Red and Pink Gold: alloy of gold, copper and a small amount of silver
  • Green Gold: alloy of gold, silver, copper and cadmium

2. Intermetallic compounds producing blue and purple golds along with other colours. These are normally brittle but can be sued as gems and inlays.

Examples of colours created from intermetallic compounds

  • Purple Gold: alloy of gold and aluminum
  • Blue Gold: alloy of gold and gallium or indium

3. Surface treatments, like oxide layers produce darker colours like black and blue.

Black Gold can be achieved through various methods:

  1. Petination (applying sulphur and oxygen containing compounds)
  2. Plasma assisted chemical vapour deposition
  3. Controlled oxidation of gold containing chromium or cobalt

Blue Gold: oxide layers can be used to obtain blue gold from alloy of gold, iron and nickel. A rich sapphire blue can be obtained alloying ruthenium rhodium & three other elements.

There you have it! A look into the history, the uses, the breakdown of karats and the plethora of colours for my precious... Gold! 


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