Gold

Gold is one of the first metals ever used by humans. We were making jewelry with it as early as 4600 BCE, with the rise of civilization. Unlike other metals, gold often appears in nature in its pure form, making it easy for early civilizations to spot and use. Across the world, ancient cultures were fascinated by this shiny metal.

It’s known as the Bronze Age, but gold artifacts first appeared in Ancient Egypt in 5000 BCE. While ancient man was developing the wheel, humans were also crafting bracelets, rings, and necklaces from the precious metal. Gold became a symbol of wealth and power, spreading across the ancient world and enabling trade far beyond Egypt, reaching as far as the Indus Valley, Anatolia, and the Balkans.

Early civilizations hammered and shaped naturally occurring gold into jewelry and ornaments. But as smelting techniques developed around 4000 BCE, goldsmiths were able to separate the metal from ores, enabling more intricate work. The Egyptians, in particular, mastered the art of alloying gold with other metals to improve its strength and alter its color, allowing for a wider variety of uses in ceremonial objects, jewelry, and even furniture. By 1200 BCE, the Egyptians were using lost-wax casting to create intricate gold sculptures, a method still used today!

Early innovations in goldsmithing laid the foundation for how we manipulate gold and other metals today. While ancient people prized gold for ceremonial and artistic purposes, modern science has expanded gold’s role far beyond decoration. Gold’s unique properties, like excellent conductivity and resistance to corrosion, make it crucial in high-tech fields for electronics, space exploration, and medicine. From circuit boards in smartphones to life-saving medical equipment, gold plays an essential role in the cutting-edge technologies of modern life. Gold's role has evolved from a symbol of beauty to a critical component of cutting-edge innovations and scientific breakthroughs.

Gold is one of the densest of all metals, is highly malleable and is a good conductor of heat and electricity. It is one of the few elements found in a natural state, as a soft metal with a characteristic yellow color. But, when finely divided, gold's color may shift to be black, ruby, or even purple.

The Purple of Cassius is a test to detect gold. Gold is inert, meaning it is chemically unreactive, but it will dissolve in in aqua regia (a mixture of nitric and hydrochloric acids). The purple pigment of the test's namesake comes about when the dissolved gold mixes with tin(II) chloride, turning the solution purple and creating a type of auric gold. Auric gold atoms have lost three electrons, giving them a positive charge. That charge determines how gold interacts with other atoms. Like a magnet, positively charged auric gold is strongly attracted to negatively charged atoms (or ions), making gold more reactive and easier to form compounds. These compounds are typically used in specialized chemical reactions, industrial processes, and sometimes in medicine, rather than in the familiar metallic form of gold used for jewelry or coins.

Around half of all gold mined today is used to make jewelry, which is still the single largest use for gold. It is used in coinage and is a standard for monetary systems in many countries. You'll even find gold in dental work and for coating things to protect them. Gold is used to coat satellites because it reflects heat well and doesn’t react with other materials, making it perfect for outer space!

Gold is found in veins of rock or in loose deposits, like sand or gravel, called alluvial deposits. To get gold out of the ground, people mine for it or use a method called panning, where they wash the dirt away to find bits of gold—you may have seen this in old Gold Rush movies with people sifting through rivers. Once the gold is collected, it’s separated from other materials through processes like cyaniding, amalgamating, and smelting (basically, heating it up to melt away impurities). Sometimes, gold is refined further using electrolysis, a process that uses electricity to purify it.

Although there’s some gold in seawater (around 4 grams in 1,000,000 tones of water), no one has figured out a way to collect it in a way that would be profitable. Almost 15,000 tons of gold is floating around in the ocean!