Gold is obtained through two main methods of extraction: pleasure and vein extraction, and also as a by-product of the extraction of other metals. All the gold found on Earth comes from the remains of dead stars. As the Earth formed, heavy elements such as iron and gold sank toward the planet's core. If no other event had occurred, there would be no gold in the Earth's crust.
But, about 4 billion years ago, the Earth was bombarded by asteroid impacts. These impacts agitated the deepest layers of the planet and forced some gold to enter the mantle and crust. In its natural form, it is found deep in the layers of the Earth, where it is carried by water, molten lava and volcanic eruptions and earthquakes. Geologists have found gold in rocks as old as 4.5 billion years ago.
The proportion of gold in the alloy is measured in carats (k), with 24 carats (24 k) being pure gold (100%) and the lower carat numbers proportionally lower (18 carats 3 75%). The advantage of using gold compared to other metals for connectors, such as tin, has been debated in these applications; audiovisual experts often criticize gold-plated connectors as unnecessary for most consumers and consider them simply a marketing tactic. The carat weight of gold is indicated by a number, followed by a “c” or “ct”, which indicates how much metal a piece of jewelry is gold. Once gold has been processed and refined, it is ready for use in any product for which it was mined, be it electronics, dentistry, aerospace or any other application of gold.
Some gold compounds have aurophilic bonds, which describe the tendency of gold ions to interact over distances too long to be a conventional Au-Au bond, but shorter than the van der Waals junction. Common colored gold alloys include the distinctive eighteen-carat rose gold created by adding copper. Gold played a role in Western culture, as a cause of desire and corruption, as told in children's fables such as Rumpelstiltskin, in which Rumpelstiltskin turns hay into gold for the peasant's daughter in exchange for his son when he becomes a princess and steals the chicken that lays golden eggs in Jack and the Beanstalk. Gold is also used in infrared shielding, the production of colored glass, the coating of gold leaves, and the restoration of teeth.
Gold also dissolves in mercury, forming amalgam alloys, and since gold simply acts as a solute, it is not a chemical reaction. The city of Johannesburg, located in South Africa, was founded as a result of the Witwatersrand gold rush, which resulted in the discovery of some of the largest natural gold deposits in recorded history. Gold has only one stable isotope, 197Au, which is also its only natural isotope, making gold a mononuclidic and monoisotopic element. Although the gold ion is toxic, the acceptance of metallic gold as a food additive is due to its relative chemical inertness and its resistance to corrosion or transformation into soluble salts (gold compounds) by any known chemical process found in the human body.
Cyanidation is the most popular and involves oxidizing and dissolving gold in alkaline cyanide and separating the resulting gold solution from solids. Only 10% of the world's consumption of new gold produced goes to industry, but by far the most important industrial use of new gold is the manufacture of corrosion-free electrical connectors in computers and other electrical devices.