Gold · element 79
The metal that never rusts, soft enough to hammer into leaf so thin you can see through it
Key facts
Gold objects buried more than six thousand years ago come out of the ground as bright as the day they were made. That single property, a near total refusal to react with air or water, explains almost everything about gold's place in history. It could be found as pure metal in riverbeds, shaped without a furnace, and it never lost its shine. So it became ornament, then money, then the standard against which money was measured.
It is also a genuinely odd metal: the only one that is yellow when pure, the most malleable of all, and its colour turns out to be a side effect of Einstein's relativity.
Where it is found
Gold is rare, a few parts per billion in the crust, but unusual in occurring as the pure metal. Hot water circulating deep underground dissolves traces of gold and deposits them in quartz veins. When those veins weather, the heavy grains wash into rivers and settle in gravel beds, forming the placer deposits that fed every gold rush from California in 1849 to the Klondike in the 1890s.
Today the biggest producers are China, Russia, Australia, Canada, the United States and Ghana. South Africa's Witwatersrand basin has yielded around a third of all the gold ever mined, and modern mines work ore containing only a gram or two per tonne. The gold itself was made before the Earth existed, in violent cosmic events such as colliding neutron stars.
A history rather than a discovery
No one discovered gold. The oldest known worked gold comes from graves at Varna in Bulgaria, dated to around 4500 BCE. Egyptian tombs are full of it, the kingdom of Lydia in modern Turkey struck the first gold coins around 600 BCE, and alchemists spent two thousand years trying to make it from lead and mercury.
The chemical symbol Au comes from the Latin aurum, meaning shining dawn. The English word gold shares a root with yellow. Its purity is still measured in carats, a system where 24 carat is pure metal, 18 carat is 75 per cent gold and 9 carat is 37.5 per cent.
What we use it for
Roughly half of newly mined gold becomes jewellery, and much of the rest is bought as bars and coins by investors and central banks. But gold also does quiet technical work: because it conducts electricity well and never corrodes, thin gold plating protects the connectors and bonding wires inside almost every phone and computer.
In medicine, gold nanoparticles produce the coloured line in pregnancy tests and rapid Covid tests, and a gold compound treats rheumatoid arthritis. Dentists have used gold for crowns for centuries. In space, a gold coating on the mirrors of the James Webb Space Telescope reflects infrared light, and gold films shield satellites and astronauts' visors from heat and glare. Architects even tint windows with traces of gold to reflect summer sun.
Reading the numbers
Gold melts at 1064 °C, lower than copper and well below iron, which is why ancient goldsmiths could work it with charcoal fires, and boils at about 2970 °C. Its density of 19.3 grams per cubic centimetre means a litre of gold weighs 19.3 kilograms, about two and a half times as much as iron. A gold bar the size of a house brick weighs roughly 12 kilograms, far heavier than it looks in films.
The electron configuration [Xe] 4f14 5d10 6s1 has a full d shell plus a single s electron, the same pattern as copper and silver, so gold sits beneath them in group 11. Its electronegativity of 2.54 is the highest of any metal, which is why it is so hard to oxidise and can even form negative ions in exotic compounds. The colour comes from relativity: electrons in such a heavy atom move fast enough that the 6s orbital shrinks, narrowing the energy gap so that gold absorbs blue light and reflects yellow. Silver, one row up, is not heavy enough for this and stays white.
Safety and the environment
Metallic gold is so unreactive that it passes through the body untouched, which is why gold leaf is a permitted food decoration. Some gold compounds, by contrast, are toxic and must be handled with care.
The environmental cost lies in mining. Extracting a few grams from each tonne of rock means enormous volumes of waste, and the two common extraction chemicals, cyanide and mercury, are both hazardous. Small scale mining that uses mercury is one of the largest sources of mercury pollution in the world. Recycling helps: about a quarter of the gold supplied each year comes from old jewellery and electronics.
Did you know?
- All the gold ever mined, well over 200,000 tonnes, would fit in a cube roughly 22 metres on each side.
- Gold is so malleable that a single gram can be beaten into a sheet about a square metre in area, and gold leaf is thin enough for greenish light to pass through it.
- Gold's yellow colour is a relativistic effect: its electrons move so fast that the energy levels shift and blue light is absorbed.
- The red or pink line on a pregnancy test is made of gold nanoparticles.
- Olympic gold medals are mostly silver, with a coating of at least six grams of gold.
- One ounce of gold can be drawn into a wire tens of kilometres long.
More in the transition metals
Column-mates come first, since elements in one column have outer electrons arranged in a similar way and tend to behave alike; the rest are the nearest neighbours in the family.
See all 38 transition metals on one page, or browse all 118 elements.
Compare Gold with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
Why is gold so valuable?
It is scarce, it never corrodes or tarnishes, it is easy to shape and to test for purity, and it has been trusted as money for thousands of years. Modern demand from jewellery, electronics and investors keeps that value high.
Is gold magnetic?
No. Pure gold is slightly diamagnetic, meaning it is very weakly repelled by a magnet. If a piece of gold jewellery sticks to a magnet, it contains other metals.
Does gold rust or tarnish?
No. Gold does not react with oxygen or water, so it never rusts, and unlike silver it is not blackened by sulfur in the air. Lower carat jewellery can discolour slightly because of the copper or silver mixed into it.
Can gold be made artificially?
Yes, in a nuclear reactor or particle accelerator, by transforming mercury or bismuth atoms. The amounts are microscopic and the cost is vastly higher than the gold is worth, so it is only ever done as an experiment.
Read next
Guess the mystery element in six tries. A new one every day, free, no sign-up.
Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Gold reference article. Spotted an error? Tell us.