In the past year, there have been frequent news reports of gold prices rising as the COVID-19 pandemic spreads in the world. When the global situation is unstable due to a global epidemic or war, people invest in gold, which is the most reliable asset. Gold has been treated as the most precious metal by mankind since ancient times and it has also been converted into money and used as a measure of value. What kind of metal is gold and why is it treated as such?

What are the properties of gold?

Gold has an atomic number of 79, element symbol Au, and an atomic weight of 196.967. It is a mineral with a yellow luster and has the greatest malleability among the minerals, spreading thinly when struck or pressed. It can be made with a thickness of less than 1/10,000 mm, so a thin layer of gold the size of a thumb can cover the entire three-story building. So, the cost of covering a building or a huge Buddha image with gold is not as high as one might expect. Even a huge building like Building No. 63 in Yeouido can cover its entire exterior with gilded glass windows. Gold has the highest ductility, which is the property of expansion among metals. So 1 gram of gold can stretch up to 3 kilometers. Gold is not only excellent in flexibility and ductility, but also has a low melting point, which makes it easy to process.

Gold is chemically very stable and does not react with other substances. Therefore, it does not corrode or rust and can be preserved in its original condition. Gold is also insoluble in acids and bases. However, it is soluble in regia water made by mixing nitric acid and hydrochloric acid, and in magic acid, which is a very strong acid made synthetically from hydrofluoric acid. In addition, gold has excellent electrical conductivity after silver among metals.

What is gold used for?

Gold is the first metal used by man after copper, and it has been used in various fields since ancient times because of its unique properties. Gold has excellent malleability and ductility, so it is easy to process, has luster, does not rust or change, and does not harm the skin at all. So, since time immemorial, people have been making gold from thin foil or thread and using it as a beautiful decoration to wear on their body.

In addition, gold did not interact with any substance in the human body and did not change, so it was used as a material for teeth. According to records, gold has been used as a dental material for 3,000 years. There is a record that the Etruscans who lived in the Italian peninsula around the 7th century BC made artificial teeth with gold leaf when they lost a tooth, and secured it with gold leaf when the tooth vibrated. Meanwhile, in the East, gold has been used as a medicine for a long time. In medical books such as Donguibogam, there are records that gold has a calming effect on the nerves. Therefore, the outer surface of Woohwang Cheongsimhwan, which is a herbal medicine used for brain and neurological diseases, is encoded with high purity gold.

Humans have always recognized the value of gold and treated it as a precious material. Then, naturally, it began to be used as currency. In the early seventh century BC, in Lydia, an ancient kingdom in what is now Turkey, amber gold, an alloy of gold and silver found in nature, was made into bean-shaped blocks and used as currency. This is the oldest coin-shaped coin ever known. After that, gold coins were used around the world for a long time.

In modern times, it is used as a material for electronic products using the properties of gold, which is easy to process and has excellent electrical conductivity. There is a circuit board on which various parts are connected to electronic products, and a thin layer of gold is coated on the parts where the parts are connected to the circuit board. Gold is also used in semiconductors. In semiconductors, a very thin metal wire is used to connect a silicon chip and a circuit board. This metal wire is made of gold and is called gold wire.

Gold is also used to build spaceships. The lunar explorer, the Apollo spacecraft, had a thin layer of gold on its surface. The film blocks radiation from space and reflects up to 98% of infrared radiation without being easily oxidized or eroded. Gold is also used in the space shuttle. The connection part between the engine and the fuselage is weak against heat, and a gold-containing alloy is used in this part to reflect heat.

How much gold is on earth?

When the Earth was formed, most of the heavy elements, including gold, sank into the Earth’s core, leaving very little gold on the Earth’s surface. At that time, collisions occurred between the bodies of the planets and the primordial Earth, which were very young planets. The elements of the planetary body did not sink into the Earth’s core and did not sink into the earth’s crust, and they dissolved in the crust and became a component of the crust. Most of the gold that exists today was created during this time. Most of this gold is evenly dispersed in rocks or cannot be easily mined by entering seawater. However, it can be easily mined if gold veins are found in which gold ore, a rock with a high gold content, is collected. Gold veins are formed when rocks containing gold elements melt in magma and then rise to the surface due to volcanic activity and cool, when heavy gold elements sink and collect.

It is said that approximately 171,300 tons of gold have been mined throughout human history. By volume it is equivalent to filling 3.5 Olympic swimming stadia. However, about half of that gold was mined within 50 years, and more than 90% of the gold currently in circulation was mined after 1848, when the gold rush began. Before that, the total amount of gold mined worldwide was only 10,000 tons. Gold is a precious metal.