Gold

Gold is a special kind of metal known as a chemical element. Its symbol is Au, which comes from the Latin word aurum. Gold shines with a bright yellow color and is very soft and bendable. It does not react easily with other substances, making it very valuable.

People have used gold for thousands of years to make beautiful jewelry, coins, and art. Even today, gold is highly valued and used in many ways, such as in investments and for making parts inside computers because it does not rust or break down easily.

Gold can be found in nature, often in small pieces called nuggets, or mixed with other metals like silver and copper. It is rare compared to other metals, but people mine it from places all around the world. In fact, if all the gold ever made were gathered together, it could form a giant cube over 20 meters on each side!

Etymology

Gold has words that sound similar in many Germanic languages. Its name comes from an old language called Proto-Germanic, which itself came from an even older language called Proto-Indo-European. The word means "to shine" or "to gleam."

The symbol Au comes from the Latin word aurum, which also means "gold." This Latin word is related to the word for "dawn," showing how people long ago thought of gold as something that shines like the morning light.

Characteristics

Gold is a very special metal. It can be stretched into extremely thin wires and can also be beaten into very thin sheets. One gram of gold can be made into a sheet that covers a whole square meter! These thin sheets can even let some light through and can block heat rays, making them useful for protecting people from heat.

Gold is also very heavy, almost as heavy as a metal called tungsten. It is a good conductor of heat and electricity, meaning it can carry these well. Unlike most metals that are gray or silver, gold has a beautiful yellow color. This color comes from its special atomic structure. By mixing gold with other metals, we can create different colors of gold, such as rose gold, white gold, green gold, blue gold, and even purple gold.

Gold has one main form that is stable and does not change, but scientists have made many other forms of gold that are radioactive and break down over time. These different forms are called isotopes. Most of these break down quickly, but a few last longer.

Main article: Colored gold

Main article: Isotopes of gold

See also: Synthesis of precious metals

Chemistry

Gold is a special kind of metal that can form many different compounds. Most often, gold shows two main types of chemical states, called Au(I) and Au(III). Au(I) is very common and is found in compounds with certain soft substances. These compounds usually form straight-line shapes.

Au(III) is another common state, seen in a compound called gold(III) chloride. In these compounds, gold atoms often form flat, square shapes with bonds that share electrons in special ways.

Gold does not react with oxygen or ozone. It can react with chlorine, bromine, and iodine to form different compounds. Gold can also mix with mercury to form a special combination called an amalgam. It stays unchanged by most acids but can dissolve in a special mix of acids called aqua regia.

Gold does not react with most basic substances. However, it can react with certain substances like sodium or potassium cyanide when oxygen is present, forming soluble compounds.

Gold can exist in less common chemical states, including -1, +2, and +5. In the -1 state, it forms stable compounds similar to some non-metal elements. Gold(II) compounds often have special bonds between gold atoms. Gold(V) is the highest known state of gold, found in a compound called gold pentafluoride.

Origin

Gold in the universe comes from special space events. It was part of the dust that formed our Solar System. Three main space events make gold: explosions called supernovae, collisions between neutron stars, and big flares from magnetars. These events use a process called the r-process to create gold and other heavy elements.

For a long time, scientists thought supernovae made most gold. But in 2017, they saw gold being made during a neutron star collision. This showed that these collisions also create lots of gold. Even so, neutron star collisions alone can't explain all the gold in older stars. In 2025, scientists found that magnetar flares also make gold. These flares happen more often and earlier in the universe's history, helping explain gold in older stars.

Most of Earth's gold likely came from asteroid impacts long ago. One famous impact may have helped uncover gold deposits in South Africa. Scientists also think gold came from deep inside Earth, from its mantle.

Occurrence

Gold can be found in rocks formed long ago, starting from the Precambrian time. It is usually found in its natural form, often mixed with silver to make alloys. These mixtures can look silvery or golden depending on how much silver is present.

Gold appears as tiny particles in rocks, sometimes with minerals like quartz. It can also be found as small pieces called nuggets in riverbeds and streams. These nuggets form when minerals break down and wash away, leaving behind bits of gold.

Sometimes gold is found together with other elements like tellurium, copper, or lead, forming different minerals. Recent studies suggest tiny living things might help create gold deposits by moving and gathering gold particles.

The world’s oceans also contain tiny amounts of gold, but there is far too little to make it worth trying to collect. Many people have tried to extract gold from seawater throughout history, but it has always proven impossible.

Seawater

Our oceans hold very small amounts of gold, but it is far too little to be useful. People have tried for years to collect gold from seawater, but these attempts have always failed.

History

Main article: History of gold

Humans have been using gold for a very long time. Tiny pieces of natural gold have been found in caves in Spain that people used around 40,000 years ago. Some of the oldest gold objects ever found are from Bulgaria and date back to around 5,000 years ago.

Gold was also important in ancient places like Egypt, Mesopotamia, and Central Europe. Later, gold helped start the use of coins in places like Lydia around 610 BC. During trips to Mecca, leaders like Mansa Musa of the Mali Empire gave away so much gold that it changed the value of gold in nearby areas.

Explorers from Europe searched for gold in places like Mesoamerica, Peru, Ecuador, and Colombia. They found gold that local people valued highly. Later, Europeans also looked for gold along the coast of West Africa, which they called the "Gold Coast".

Production

Main article: List of countries by gold production

In 2016, about 5,726,000,000 troy ounces of gold was recorded, and 85% of it is still being used today.

Mining and prospecting

Since the 1880s, South Africa has provided a lot of the world's gold. In 2007, China became the top gold producer, taking over from South Africa. In 2023, China was the leading gold-mining country, followed by Russia, Australia, Canada, the United States, and Ghana.

In South America, there is a project called Pascua Lama in the high mountains of the Atacama Desert, at the border between Chile and Argentina, aiming to extract gold from rich fields there.

It is estimated that up to one-quarter of the world's yearly gold production comes from small or individual mining efforts.

The city of Johannesburg in South Africa grew because of the Witwatersrand Gold Rush, which found some of the biggest gold deposits ever known. These gold fields are in the northern and north-western parts of the Witwatersrand basin, a thick layer of old rocks deep under Free State, Gauteng, and nearby areas. Some mines here go down almost 4,000 metres, making them some of the deepest mines on Earth. The gold is found only in certain areas where old rivers once flowed into a sea.

The Second Boer War of 1899–1901 between the British Empire and the Afrikaner Boers was partly about who could mine and keep the gold in South Africa.

During the 1800s, many gold rushes happened when big gold deposits were found. The first known gold discovery in the United States was at the Reed Gold Mine in North Carolina in 1803. Major gold rushes later happened in California, Colorado, the Black Hills, Otago in New Zealand, many places in Australia, South Africa's Witwatersrand, and the Klondike in Canada.

Grasberg mine in Papua, Indonesia is the largest gold mine in the world.

Extraction and refining

Gold extraction works best in large, easy-to-mine areas. Even very small amounts of gold, as little as 0.5 parts per million, can be worth mining. In open-pit mines, ore usually has 1–5 parts per million of gold, while underground mines need at least 3 parts per million. Because gold is usually too small to see with the naked eye in most mines, it is hidden inside the rocks.

The cost to mine and prepare gold was about $317 per troy ounce in 2007 (which would be about $492 in 2025), but this can change a lot depending on how the gold is mined and the quality of the ore. In that year, the world produced about 2,471.1 tonnes of gold.

After being mined, gold is often made even purer using methods like the Wohlwill process or the Miller process. The Wohlwill process uses electricity, while the Miller process uses a special chemical mix. Other ways to clean small amounts of gold include using heat or dissolving the gold in a strong mix of acids.

Recycling

In 1997, about 20% of the gold sold came from recycling. Companies such as jewelry makers and computer makers like Dell take old gold items and reuse the gold.

By 2020, making new gold by mining creates 16 tonnes of carbon dioxide CO₂ for each kilogram of gold, while recycling gold creates 53 kilograms of CO₂ for each kilogram. About 30% of the world's gold now comes from recycling, not from new mining.

Pollution

Further information: Mercury cycle and International Cyanide Management Code

Getting gold can sometimes harm the environment.

When ore has very little gold, it is crushed and mixed with a chemical to help get the gold out. This chemical can be very dangerous and has caused harm to water and animals in rivers near mines. These events are considered major environmental problems. Large amounts of waste from mining can also pollute water with heavy metals.

In the past, mercury was used to find gold, but today it is mostly only used by small miners. Even tiny amounts of mercury can hurt fish and animals in water, and can also affect people who eat the fish.

Getting gold also uses a lot of energy — it takes about 25 kWh of electricity to get one gram of gold.

Monetary use

Further information: History of money

Gold has been used around the world as money. People use it to trade for things instead of swapping items directly, and to keep wealth safe. Special places called mints make gold coins, bars, and other pieces that all weigh the same and are very pure.

The first gold coins were made in a place called Lydia, in Asia Minor, about 600 BC. Later, many countries started making their own gold coins. In the 1800s, many countries used gold to back their money. After World War II, most countries stopped using gold for money and started using paper money instead. But some banks still keep gold to show they have wealth.

Today, people still buy and sell gold, and its price changes often. Gold is measured in units called karats, with 24 karats being pure gold.

Price

Gold is measured by weight and by how pure it is. The purity is called karats, with 24 karats being completely pure gold. The price of gold changes every day based on how much people want to buy or sell it.

Other applications

Jewelry

Pure gold is often mixed with other metals to make jewelry. This makes the gold harder and changes its color and other properties. Different mixes, called alloys, can make gold into various colors and strengths, like 22-karat or 18-karat gold. Gold can also be shaped into thin threads and used in special sewing.

Electronics

Gold is very important in electronics because it does not rust and conducts electricity well. It is used to coat parts in computers and other devices to make sure they work well. For example, a typical cell phone contains a small amount of gold. Gold is also used in important connections for audio, video, and USB cables, especially in high-end products.

Medicine

Gold has been used in medicine for a long time. Some gold compounds are used to treat arthritis and other conditions because they reduce pain and swelling. Gold is also used in dentistry for making strong and lasting tooth crowns and bridges. Tiny gold particles are used in research to study cells and materials.

Cuisine

Gold can be used to decorate food and drinks. It is safe to eat because it does not change the taste or nutrition of food. Historically, gold has been used to decorate sweets and special drinks, like a traditional German liqueur that contains gold flakes.

Miscellanea

Gold has many other uses. It can change the color of glass, reflect heat and light, and is used in satellites and special suits for astronauts. It is also used in some car parts to protect against heat. Gold can be made very thin and transparent, and it is used in some aircraft windows to prevent ice from forming.

Toxicity

Pure gold is safe and does not harm the body when eaten. It is sometimes used to decorate food, like a thin sheet called gold leaf. Gold is also found in some special drinks such as Goldschläger, Gold Strike, and Goldwasser. It is allowed as a food additive in the EU, listed as E175 in the Codex Alimentarius.

However, some gold compounds can be harmful to the liver and kidneys. For example, gold chloride and certain cyanide salts used in electroplating are toxic. In very rare cases, these can be dangerous. Special medical treatments can help treat such poisoning.

Gold can sometimes cause skin reactions in some people, especially women, but it is less likely to cause problems compared to metals like nickel. Some fungi, like Aspergillus niger, have been found to interact with gold and other metals in mining solutions.