The Life Story of Gold

In its purest form, gold is an element, with the designation Au on the periodic table and the atomic number of 79. Metals are the heaviest elements, and gold is the heaviest of all.

Evidence from the Vredefort crater in South Africa indicates that much of the accessible gold supply came to Earth from a meteor about 2 billion years ago.

Like most heavy metals, gold is created inside stars by nuclear fusion. Following the Big Bang, only two elements were formed: hydrogen and helium. A few hundred million years later, these first stars were burning with nuclear fires that forced lighter elements together to make slightly heavier elements such as carbon, nitrogen, and oxygen, and these nuclear reactions released a huge amount of energy. The result were titanic explosions known as supernovas, which left only their dead cores now known as neutron stars.

Gold was born when two neutron stars collided. They were “moving almost at the speed of light around each other,” says Brian Metzger, astronomer at Columbia University, “and then they slam into each other. As the matter expands there are nuclear reactions, which turn the neutrons and protons into heavier nuclei like gold and silver and platinum.” The debris from this collision became meteorites packed with gold and other metals which bombarded Earth.

Astronomers estimate that the neutron star merger observed in August 2017 would have created between 10 and 100 Earth masses’ worth of gold.

Where Is It?

Oceans are the greatest single reservoir of gold on Earth’s surface, containing approximately eight times the total quantity of gold mined to date.

But most of the Earth’s gold is in its core—some 1.6 quadrillion tons of it, enough to pave the planet with one and a half feet of solid gold.

The best estimates currently available suggest that around 190,040 tons (or 172,400 metric tonnes) of gold have been mined throughout history—of which two-thirds have been mined since 1950. Another estimate lowers the figure to 167,550 tons (or 152,000 metric tonnes), an amount that would fill just 60 tractor trailers. Either way, it’s been stated that all the gold ever found would fill only two Olympic-sized swimming pools.

Each year, gold mining adds approximately 2,500 to 3,000 tons to the world’s stock of gold. The United States is the world’s third-largest gold-producing country, after South Africa and Australia. Mines in Nevada — about half of the active mines in the U.S. — account for more than 80 percent of U.S. production.

The Federal Reserve Bank of New York holds the world’s largest accumulation of monetary gold: $147 billion worth of gold bullion in a vault 80 feet beneath the street.

Gold’s Golden Qualities

Gold is chemically inactive, and is extremely resistant to chemical action. It cannot be dissolved by any substance other than Aqua regia, a mixture of nitric and hydrochloric acids. It doesn’t rust or tarnish, is soft enough to be easily worked by beating or drawing into wire, alloys with many other metals, and can be melted and cast into highly detailed shapes. It can be reused and recycled. All of these properties could be harnessed in ancient times, as today, just by heating gold nuggets at high temperatures and using simple tools such as hammers or molds.

Pure gold is always a bright, rich yellow; any other colors, such as rose, green, or white, are the result of alloying it with other metals.

A warm yellow in its pure form, gold becomes a bright yellow when combined with between 5 and 30 percent silver. It takes on a pale, greenish-yellow tone with 30 to 50 percent silver, and starting with 50 percent silver it becomes white (i.e., “white gold”).

When pure gold is mixed with copper, starting at 5 percent, it becomes reddish; starting at 30 percent copper it takes on a copper shade. As little as 5 percent of palladium gives gold a cold yellow shade.

Electrum is a naturally occurring alloy of gold containing more than 20 percent silver, as defined by Pliny the Elder in his Naturalis historia. The gold used by the Egyptians generally contains silver, often in substantial amounts, and it appears that for most of Egypt’s history, gold was not refined to increase its purity.

Karats or Carats?

“Karat” means the relative amount of gold in an alloy, while carat is a unit of weight (200 milligrams).

24-karat gold is 100 percent gold;

18-karat___________75 percent

14-karat___________58 percent

12-karat___________50 percent

9-karat____________37.5 percent

Uses of Gold

Jewelry: From 50 to 80 percent of new gold used each year is in jewelry. India is the world’s largest consumer of gold jewelry. South Asian jewelry is generally of higher purity than Western jewelry — 22 karats compared to 18 or 14 karats.

Industrial: About 12 percent of the gold used each year goes to electronics, medical, and dental uses. Solid state electronic devices use very low voltages and currents which are easily interrupted by corrosion or tarnish at the contact points. Due to its exceptional electrical conductivity, and its resistance to corrosion, a small amount of gold is used in almost every sophisticated electronic device.

Investment: The remaining 10 percent each year is used for investment purposes, coinage, and bullion.

Aerospace: All space equipment uses gold. Gold particles act as a form of lubrication on satellites and other aerospace equipment. And in certain NASA telescopes, the mirrors are coated with gold.

The visors of astronauts’ space helmets receive a coating of gold so thin (0.00005 millimeters, or 0.000002 inches) that it is partially transparent. The astronauts can see through it, but even this thin layer reduces glare and heat from sunlight.

Chemistry: For centuries, alchemists attempted to produce gold by transforming it from base metals using the “philosopher’s stone.” First attempts were made in China in the 4th century B.C. and also in ancient Greece, thereby laying the foundations of modern chemistry.

Health: Gold has been used in dental work for more than 3,000 years. The Etruscans in the 7th century B.C. created a type of denture using gold wire to fix substitute animal teeth in place. Gold has also been used (or marketed) for a variety of health issues. For the truth on those fronts, see our sidebar, “Gold as a Rejuvenator: Myths vs. Facts”