No one knows exactly which millennium BC it was when somebody first saw and coveted a shiny piece of metal that shimmered like dawn’s first light and yet was solid enough to turn dreams into reality.
Today gold is so integral to our world that we will have to look at it in three parts. Today we’ll focus on its history and use in jewelry.
In part 2 we’ll look at the many practical uses of gold today. Then in part 3 we’ll find out where it comes from (hint: it (edit) probably comes from space, just like platinum) .
The color of gold
The value of gold lies in its appearance. Let’s just admire it for a while.
It’s hard to believe. but the theory of relativity is behind that gorgeous color.
Electrons are those little particles that were diagrammed back in my day as orbiting around an atomic nucleus. Let’s wait until next week to talk about them in detail. For now, let’s just say that electrons in an atom of metal don’t do orbits.
In gold, as in all metals, electrons oscillate. This rapid movement is in the ultraviolet range for most metals.
Small particles moving at high speed – sounds like we’re getting Einsteinian here.
We are. In gold and cesium, subtle relativististic effects on these fast-moving electrons take the electron oscillations out of the ultraviolet and into the visible range of the spectrum. To us, it appears as a attractive sheen (cesium looks pretty cool, too).
The history of gold
Some 5,600 years ago the Egyptians were smelting gold, which was said to be very common in in the region, particularly in the Upper Nile and the Nubian Desert. A thousand years later, around 2600 BC, the Mesopotamians made the first known gold jewelry.
Around 1000 BC, the traders of India, where gold was used in dowries, referred to Southeast Asia as “the land of gold.”
The first known gold coins (actually electrum – a mixture of gold and silver) appeared in Lydia, Asia Minor, around 600 BC. Not coincidentally, the Lydians were also the first to establish retail shops in permanent locations.
Various other ancient currencies also used gold coins (Italian language).
This history is by by no means complete, but it looks to me that, in Africa, starting at around the 10th century AD, the Sultanate of Mogadishu controlled the East African gold trade from Africa, southern Asia, and even as far as away as China.
European traders eventually also became involved, and the trade spread westward and north, across the Sahara, to supply this new market.
Europe had been using silver as currency but switched to gold in the 13th and 14th centuries. Portugal began to expand as a power in the early 15th century after it took Ceuta, on the north coast of Africa, to control the Saharan gold trade.
Of course, gold was also on the minds of Spanish conquistadors and English colonists alike as they headed for the New World.
China was using paper currency by the beginning of the 10th century, but it was based on bronze and copper rather than gold.
By the 19th century, paper money that could be converted through various ways into gold was common in the the West. The use of such currency didn’t completely die out until 1999 when Switzerland joined the International Monetary Fund and switched to the fiat currency everybody else was using.
Karats or carats?
The gold:alloy proportion in an object is measured in karats. Pure gold is 24 karats (not carats – that unit is used for gemstones).
Circulating gold coins had to stand up to wear and tear, so they were alloyed to make them harder. Those in use from the 16th through the early 20th centuries were generally 22 karats (American coins were 21.6 karats).
In the Wild West, by the way, people did indeed check a gold coin by biting it, but it wasn’t gold’s softness they were looking for. They wanted to make sure it was a real coin (hard), not electroplated lead (soft).
Today’s gold coins are only used for collecting and investment, so they can be the softer 24 karats.
Gold is the most malleable of all metals – it can be hammered, for example, into thin gold leaf. It’s also the most ductile and be stretched into thin strands that make a beautiful filigree. These properties make it popular in jewelry and the arts.
Like coins, jewelry needs to be durable. Gold used in jewelry therefore is generally not more than 14 karats. To color gold, just add various alloys – these are different than those used to just harden it.
Gold-filled jewelry or rolled gold plate is made of an alloy coated with gold. It has to be at least one-twentieth gold by weight. In the US, the fineness of gold used in this process must be at least 14 karats, but some countries have lower limits.
Electroplated gold must have at least seven-millionth of an inch (0.18 microgram) of gold on significant surfaces. Anything less than that is called “gold flash” or “gold washed.”
Gold is present in many levels of our world today. Books have been written just on its history or use in jewelry. This is only a brief overview. Gold is also useful in industry and medicine, as we’ll see next week. For now…
…Oh, let’s just admire it some more.
- Gold. (PDF) United States Geological Society
- Gold. Wikipedia
- History of Africa. Wikipedia
- Gold. WebElements.com