Chemical and physical properties of gold:
Crystal system: face- centered cubic
Mohs scale hardeness: 2,5
Specific gravity: 19,32 g/cm³
Melting point: 1064,2 °C
Gold is the oldest known precious metal, called lantine aurum
As a consequence of its favourable chemical properties, its good looks, its ease of working and its difficulty of extraction, it has been a common measure of value throughout history.
Use of gold
Gold is a very common mineral, but only in small quantities.
In its solid state, its brilliant yellow colour does not change when exposed to air and acids.
Easy to work, it can be stretched into soft, almost infinitely thin sheets, making it translucent.
Because of these excellent characteristics, it is used to make jewellery, precious objects, to coat and decorate metals of lesser value and as a measure of the value of the exchange of economic life.
The most important currency metal
In addition, gold is used in many other areas: medicine, health care, e.g. to make medicines, dental prostheses, electrical industry, e.g. to make electrical contacts, communications equipment.
What is real gold?
Literal pure gold is not used as jewellery, as 100% or 24 carat gold is too soft to be used as jewellery. Jewellers usually work in 14 carat (585) and 18 carat (750) gold, with 14/24 and 18/24 parts of gold respectively, and the units of measure are 585 and 750.
|Carat||Hallmark||Parts of Gold||Purity %|
(The carat has been used since about 1300. In the United States, 10 carats is the minimum gold content, but half a carat of error is allowed, so a 10 carat item may be only 9.5 carats and contain 39.6 weight percent gold. In England, gold jewellery must be at least 9 carats and in France at least 18 carats.)
The composition of the alloy is not indicated by the carat designation
Gold articles of different colours contain different alloying elements. Usually the following metals are used to achieve the different colours (the slightly greenish, green-gold alloy is rarely used):
|Type of gold||Components of the alloy|
|Yellow gold||Gold (Au)||Copper (Cu)||Silver (Ag)||Zinc (Zn)|
|White gold||Gold (Au)||Copper (Cu)||Nickel (Ni)||Zinc (Zn)|
|Rose gold||Gold (Au)||Copper (Cu)||-||-|
|Green gold||Gold (Au)||Silver (Ag)||-||-|
Gold alloys are tested by acid test
Metals containing less than 9 to 10 carats of gold will quickly turn green when exposed to nitric acid.
Alloys less valuable than 18 carats can be tested with chalybeate water (a mixture of about the same amount of nitric acid and hydrochloric acid): the metal in contact with the acid droplet immediately turns pale yellow because the colouring alloying elements are dissolved out. The test is often carried out with a touchstone: a small amount of metal is rubbed off the surface of the hard black stone and the test is carried out here, and the jewellery is polished again to flawlessness.
What causes the yellow colour of gold
Gold atoms have an unusually high nuclear charge, which accelerates the electrons to high speeds. The electrons become more massive and their orbits contract (the so-called relativistic effect). As a result, the atoms absorb light in the visible range (unlike silver) and the element appears golden. This is partly why gold is favoured.
When gold causes an allergic reaction, it is always one of the alloying metals, usually nickel, that is to blame.
Some people have an increased sensitivity to this metal. The sensitivity is usually revealed when gold-plated earrings are worn. Since the gold layer is very thin and usually overlays a layer of nickel, it is not surprising that the wearer of the earrings may also come into contact with the nickel for a long time as the gold wears off. However, the body can learn from previous contact how to react to these ions. Gold with a gold content of 14 carats or more should not discolour the skin. Jewellery with a lower gold content, but especially gold-plated jewellery, can do so.
Some interesting facts
An unusual bacterium, Thiobacillus ferrooxidans, breaks down sulphide ores and releases the gold (the bacterium is strange because it prefers an acidic environment). Some plants, such as Indian mustard (a distant relative of cabbage), will absorb gold from the soil if the soil is sprayed with ammonium thiocyanate. The reagent forms a complex with the gold.
Extraction and deposits of gold
It is hidden in cracks in the rocks, in fissure fillings, so-called veins or hollows, mostly in the form of ore, mostly in the form of ore-gold or mixed with other minerals. These are the primary occurrences, which are thought to have originated from the rising volcanic steam of molten, fiery, glowing material lying deep within the earth. They are mostly found in volcanic rocks, where quartz and sulphuric sand are the most common constituents.
For a long time it was known only in the form of gold ore and it was only at the end of the 18th century that its ores were first recognised in our country, in which it is found mixed with a hitherto unknown hemisphere, tellurium. We now know that, even in the form of gold ore, it always contains more or less other metals: silver, mercury, copper or other rare metals, which have a significant influence on its colour and hardness.
Most gold is found in secondary locations, in debris accumulations that have accumulated from gold-bearing rocks in rivers, seas and ice shelves. It is in these layers of gravel and sand that gold, which is resistant to weathering and decay, occurs as fine dust, in small or large grains or in pieces weighing several kilograms. Such places were the Eldoradoes of gold production and exploration, from which gold was extracted by washing, while gold ores were crushed from the hard rock-embedded placer ores by hard laborious mining. Secondary occurrences are currently found in the richest gold deposits in South Africa, which are interbedded with marine strata, occurring in cemented, coarse, abraded rock fragments, conglomerates.
Gold is also found in the seas, but it is so uneconomic to extract it that it is not mined.
The first record of gold is found in the Bible, where the description of paradise, along the Pison River, refers to the Khavilla region, where gold is found. This province is probably identical to the later Colchis of the Greeks. In the ancient countries of Eastern civilisation, ores were already known four thousand years before Christ, gold being the most important of them. The descriptions of the fabulous treasures of the Phoenicians, Persians, Babylonians, Carthaginians, King Solomon and Egyptians, and of the wealth of gold, are evidence of this. Gold was also the foundation of Rome's world power.
Initially they did not have much gold, because in 388 BC there were only 345 kilograms of gold in the Roman treasury. However, with the conquest of Carthage and the conquest of Mithridates, Pliny estimates that Rome was already receiving 7000 kilograms of gold a year.
Carthage drew from the treasures of Spain's prehistoric gold mines the strength to resist Rome's conquest for a century and a half. After the conquest of the Spanish mines and the conquest of Greece, the famous gold mines of Transylvania and Dacia were exploited, which from Roman times onwards have been the richest gold-producing areas in Europe.
A new era in the history of gold begins with the discovery of the Americas and the glittering of the fabulous treasures of the Incas.
The gold-bearing lands, only superficially exploited by the Incas and Indians, opened a new chapter in the history of gold. In 1848, the expansion of a small sawmill on the banks of the Americanos River in California revealed rich gold-bearing deposits. This led to an unprecedented popular movement, which history has recorded as the gold rush. All life in the city of San Francisco came to a standstill and almost everyone flocked to the gold fields.
The golden land was the foundation of many great fortunes, but more importantly it became the scene of much more suffering, misery, violence, immorality and tragedy. Almost at the same time, the gold rush in Australia was renewed with similar folly and restrained human passions, and was repeated in 1885 with the discovery of the aforementioned Witwateis Rand deposits. But it was surpassed in 1896 by the horrors of Alaska, where the goldfields were discovered frozen in ice.
The gold rush was at its peak when a particularly large nugget was found in one area or another. One such lucky find in 1869 was the 85 kilogram nugget in Australia and another 62.2 kilogram nugget of pure gold.
But the feverish exploration that follows also transforms uninhabited, unknown territories, barren deserts, into cultural areas, and so, not least, gold has contributed to the spread of man on Earth. More recently, there has also been a fairly significant migration of people to the gold fields of the Amur and Yenisei rivers in Siberia.
Despite the adventurous and often fantastic scale of gold production, the value of gold has remained relatively stable. This is why it is used as a measure of the value of economic life in all countries. Production, which has been gradually declining in recent years, has never affected the market price of gold, despite its variable annual volume.
European mines are largely depleted, having lost their importance before the discovery of rich gold fields in the Americas, Africa and Australia. Europe as a whole is hardly considered a gold-producing area today, with only the area around Boliden in Sweden having been discovered in recent years as a potential global gold deposit. Ore extraction started in 1932 and yields around 200,000 tonnes per year, with an expected gold output of 5-6,000 kg. At this rate, it ranks 51st among the 86 largest mines currently in operation.
Hungary, which before the war accounted for about 10% of European gold production, lost its most important gold mines, including Transilvania. However, immediately after the peace treaty, the search for more gold began, with some success. The Schmidt brothers, on the suggestion of Dr. István Vitális, a university professor, reopened the formerly worked Recsk mine near Parád. The mine was later taken over by the Treasury and produced 82 kg of gold in its first year of full operation, 1932. The amount of ore discovered is about 9 million q, which is enough to ensure mining for 25-30 years on today's terms.
Since the discovery of the Transvaal goldfields, the centre of gravity of gold production has shifted to Africa, where it remains today. The amount of gold ore discovered in the Witwatersrand area is more than 90 million tonnes, with a gold grade of at least 10 g/t. These mines have for many years supplied almost half of the world's total gold production, some 300-350 thousand kg per year. The British also have the Canadian gold deposit, which yields 80-90,000 kg per year, and the Rhodesian deposit in Australia (20,000 kg), so that 70% of the production goes to the British Empire. The United States (70. 000 kg) and Russia (30. 000 kg) also produce significant quantities. The amount of gold produced is constantly increasing the world's stock, the total being P57 billion in 1913, P70 billion in 1927 and P78 billion in 1930. 2 billion, of which P26.3 billion is held by the United States, P10 billion by France, P6-7 billion by England and P10 billion by the Indian treasures.
The biggest problems in gold mining
85% of the gold unearthed today will be sold as jewellery tomorrow. Gold mining does not meet basic needs, is environmentally unsustainable and socially unjust. The impact of global gold mining on local economies and the environment is at least as damaging as industrial logging or agriculture.
The 66% of gold deposits discovered deep in the mountains further worsen the situation for people and the environment. This is illustrated by some of our examples below.
All previous gold rushes have brought death and destruction to the local population through fortune hunters. The Maya believed that the Spanish conquistadors were eating gold. The California Indian population was decimated. First because of diseases brought in by the 49ers, and later because of the bounty imposed on the natives by the new California state government. In 1851 alone, the new government paid out a million dollars from its gold revenues for the scalps it had surrendered. Today, tribes in the Amazonian rainforest, such as the Yanomami and the Macuxi, the Galamsey of West Africa and the Igoros of the Philippines are under the same threat.
Landfills at sea
Companies get rid of poisonous jellyfish and zaggy fish by dumping them in the water, endangering the marine life of oceans and seas. It releases heavy metals and cyanide, poisoning fish and other food sources for people in the area. Subsea dumping of jellyfish has been banned in the US and Canada because of its destructive impact on the ocean. However, even with this knowledge, Newmont lied to the Indonesian government that the process was allowed in the United States. Newmont operates the Nusa Tengarra gold mine on the island of Sumbawa. Since 1999, the company has been dumping 120,000 tonnes of sewage into Senunu Bay every day. Before the mining started, people in the bay were catching more fish than they needed. The surplus was sold in local markets. Since Newmont has been dumping sludge into the bay, fish numbers have declined and some species have disappeared completely. The daily catch is not even enough to feed the family, and the local economy, which relied on fishing, is collapsing.
Damage to water and waterholes, the most destructive environmental impact of gold mining. This was the case in the Sierra Nevada in 1850, and it is still the case today in the Pemon lands of Venezuela. The rivers have been destroyed by gold panners, who use high-pressure jets of water to divide the riverbanks so they can sift the soil for gold. Modern gold mining is even more destructive. Gold mining in Nevada consumes more water than the entire population of the US. Groundwater levels have dropped by more than 300 metres around one open pit mine in northern Nevada, according to the US Geological Survey. One mine consumes 378 million litres a day, more than the city of Austin, Texas. The Rain mine, owned by Newmont, in Nevada, has polluted three kilometres of the Dixie Creek river with arsenic and mercury. Also Newmont's mine in Nevada, Hollister, has implemented an acid mine drainage method that contaminates groundwater with sulphuric acid - probably intended to be a continuous operation.
To make a wedding headband, you need to move at least 2.8 tonnes of soil. Gold mining produces huge amounts of waste compared to the final product. According to the Worldwatch Institute, the 2,402 tonnes of gold produced in 1997 resulted in 725 million tonnes of scrap, full of heavy metals, acids and solvents. In the US, the ratio is 1 to 3,000,000, meaning that producing one tonne of gold produces 3 million tonnes of bear. Most of this carelessly disposed of dirt is exposed to the effects of the weather and ends up polluting the environment with acids and heavy metals, causing enormous environmental damage.
The rights of indigenous peoples
The United States is the world's second-largest gold producer, with more than 70% of its gold extracted from indigenous lands. The Western Sosons, whose traditional habitat covers much of Nevada, are the forced "hosts" of three dozen open-pit gold mines. More than one of which, miles wide and miles deep, are present with poisonous puddles at their bottoms. The Western Sosons are continually denied the right to exercise their treaty rights to the land because the United States prefers to hand Nevada over to multinational mining companies rather than to its rightful owners. The story is being repeated in other parts of the world. In Ghana in the mid-1990s, thousands of farmers were evicted and relocated to carry out a World Bank-funded mining project covering hundreds of square kilometres. It is estimated that about 50% of the gold extracted over the next 20 years will come from indigenous areas.
Cyanide is the favourite chemical of mining companies to extract gold from ore. Ore with low gold content is crushed, stockpiled on the ground and injected with a cyanide solution. No mining company has ever prevented cyanide-contaminated water from seeping into the ground and damaging wildlife. In 1998, a massive cyanide spill in Kyrgyzstan killed 4 people and led to the temporary displacement of thousands of people from a Canadian-owned mine not far from the site. Near the Summetville mine in Colorado, taxpayers have spent some $100 million over the past few years to divert contamination spilled into the water of nearby rivers to at least one reservoir. Meanwhile, a spill at the Omai mine in Guyana, contaminated with billions of litres of cyanide, has killed scores of fish and other animals.
Mercury has been used for centuries to extract gold from ore by chemical means. This caused enormous damage to the health of the miners and the local population. During the California gold rush, 7,600 tonnes of mercury was dumped into local rivers and lakes, a deadly poison. It caused neurological disorders and numerous deaths in people exposed to it. At the time, mercury poisoning was known as "mad hermit disease". Half of the current mercury contamination in San Francisco Bay is a legacy of the 1849 gold rush. Beyond that, millions of fortune hunters have used mercury, from the Amazon - where it has flooded Indian reservations - to the Philippines, where it has caused the worst epidemic in recent history, so-called Minamata disease, and other horrors. More than 30% of the 500,000 "garimpeiro" (miners) tested in Brazil had levels of mercury in their bodies above the WHO limit.
The waste and pollution of water, the destruction of habitats and wildlife, the industrialisation of pristine areas, road construction and the release of huge amounts of pollutants into the environment all have a detrimental effect on the natural and human environment around gold mines. Mines carry away and break up more soil in the world than all the rivers on earth due to natural erosion. The impact on wildlife is almost incalculable, but between 1980 and 1990, in California, Nevada and Arizona alone, 7,000 dead birds were found around cyanide-contaminated gold mine ponds. This is not the tip of the iceberg when it comes to gold mine-related mortalities.