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What is gold?
The gold is a noble metal , which means it has the ability to resist oxidation (few chemicals can attack) and corrosion (it does not rust like iron). It is precisely because it has these properties that it can remain immersed in seawater, buried under the ground or exposed to the open air without being altered, and retaining its original appearance.
It is however attacked by chemical agents such as bromine, aqua regia, chlorine, selenic acid, ferric chloride, alkaline cyanides, sulfuric acid (when it is mixed with other agents oxidants).
It is also the most malleable and ductile (it has the ability to deform without breaking) of all metals used to date. Its malleability allows him especially, when he is not alloyed with another metal, to be stretched to infinity, to be easily shaped, and to be crushed. It is also for this reason that in jewelry it is often used associated with other metals, to prevent it from being deformed.
Gold is designated in different ways: the usual name thus corresponds to a chemical symbol (Au) used in particular in the periodic table of the elements of Mendeleyev.
The word gold comes from the Latin aurum , auri (neutral), which means gold, but also objects made from this precious metal , or even (gold) coins. In French, aurum gave the adjectives auriferous (of the Latin adjective aurifer , which contains gold), aurific (which produces gold) and aureux (used in chemistry to speak of monovalent gold salts).
Words such as aurora, halo, hoarding or thesaurus have also been formed from this radical, and if the semantic link with the radical has become somewhat distended, it is always present.
The substantive halo (from the Latin aureolus , which is the diminutive of aureus ) is thus used to designate the luminous circle painted around the head of the Saints in the religious representations, most often of golden color, and by extension the luminous halo around some objects reflecting or emitting light.
The name aurora (from Latin aurora ) is used to designate the first light of day, before the sun rises. These gleams being golden, the link with gold is explicit.
The Latin word thesaurus (itself derived from ancient Greek) gave the verb to hoard (save), as well as substantives thesaurus and treasure in French.
The substantives goldsmith , goldsmith (who designate the one who forges gold and its activity) and treasures are also part of the same family of words.
The density of gold is 19.3. We establish the density of a material with respect to water, which means that it is 19.3 times heavier than water. (To calculate the density of gold, it suffices to calculate its density, which is the volume (expressed in cm3) divided by the mass (expressed in grams).
In the native state, gold is very often in the form of nuggets, which are these small rounded and crushed masses, usually of small size, which can range from a few grams (for the most common) to several dozen kilos (for the rarest). It can also be found in the form of powder, also called gold sands, or in the form of yellow flakes more or less dark (depending on the impurities they contain). Finally, it can also be in the form of ore.
Gold is contained in two main types of deposits: the so-called “veins”, or veins, which are primary deposits of gold-bearing rocks, where the ore is particularly pure and may be at various depths. These deposits are located in hard rocks, not eroded, of many kinds: in volcanic magmatic rocks (such as basalt, rhyolite, andesite or serpentinite), in sedimentary rocks (such as slate or sandstone) finally, in grainy igneous rocks (such as diorite or granite).
The primary deposits were formed at extremely different times: while some were formed between 3 and 2.5 billion years ago, others would have appeared around 600 million years, others would be is barely a million years old.
Different rocks can therefore host gold, although there are minerals and soils of predilection. Quartz is thus a mineral within which gold can be found in greater or lesser concentration. Some mines only target the exploitation of one or more quartz veins, and clear the rocks that prevent its exploitation so that the ore can be extracted better, which will then be processed to release the gold it contains.
At the time of planet Earth formation, gold was at the boundary between the molten magma and the earth’s crust, at a depth of about 30 km. Over time geological movements have allowed molten fluids, from the depths of the earth, to rise to the surface, bringing with them gold, which, when these fluids have cooled and crystallized (especially under the form of quartz), remained a prisoner of these rocks, which became these veins that are exploited today.
Many gold veins are found near volcanoes because, near the crater that expels molten magma, fluids from deep regions of the Earth’s layer can also be expelled through cracks where they will form as they cool. veins that may contain gold.
Then come the secondary deposits, which are alluvial formations, located on the surface. Following geological movements, some veins can indeed rise to the surface and be exposed to the weather, which will erode these veins. The alluvial formations are formed from the erosion of primary deposits, which release flakes of the precious metal that follow the movements of the soil or scatter in the streams.
Depending on their situations in relation to the primary deposit, the secondary deposits may be called eluvium (if they remain trapped and agglomerated near the vein from which they were extracted by erosion phenomena), colluvium (if they are carried further downstream by gravity, the movements of the soil and are concentrated in folds of the relief), or alluvium if they are carried by the rivers or rivers of which they follow the course. They can then settle in the bed of these rivers or lakes. These three phases are part of the same process, which pushes minerals to the surface and disintegrates them to their alluvial form.
It is, moreover, in alluvial deposits that gold is chiefly collected. These deposits testify to the presence of a hard rock containing a vein which would have been eroded.
The deposits exploited by the mining industry
Nowadays, with the advancement of technology, which improves the extraction of ore, one can exploit a subsoil that contains only 10 grams of pure gold per ton of ore. It is usually in the form of small particles, difficult to discern from their environment with the naked eye, and mixed with sulfur or iron.
Gold is a metal that is not made. Unlike steel, which is an alloy derived from human industry, it can be found as such in the natural state, hence its rarity and mining. But, still in the native state, one can also find it mixed with other metals, like silver, in which case it forms a natural alloy called electrum.
The oldest gold artifact
It is extremely difficult to attribute the discovery of gold to a specific people. There is only conjecture in this matter, and the scientific research conducted so far to determine the earliest traces of the use of the precious metal has provided provisional dating and locating, which may be reinstated. question at a later discovery.
To date, the oldest gold was discovered in 1972 in the necropolis of Varna, the name of the city currently located in Bulgaria, on the shores of the Black Sea (in Southeast Europe). Among the objects from the 300 graves listed in this necropolis, human bones, pottery, statuettes dedicated to worship, flint made and objects made of gold between 4600 and 4200 years before our era.
The global distribution of ore depends on many factors, historical, economic, geological and even geopolitical. Thus, the distribution of gold deposits is relatively uneven across countries, even though gold is present on all continents. On the other hand, the countries with the largest mineral resources are not systematically the countries with the largest stocks. Significant movements take place and the sale of resources
Here is the list of the top 10 gold producing countries, ranked by order of decreasing production.
In 2014, mining operations totaled approximately 3133.33 tons of gold extracted from the ground.
These production volumes, which are higher than those of previous years, are proof that a net and continuous development of global extraction in the territory of many powers, which are equipped with state-of-the-art technology, while it is declining in other territories.
However, with known resources estimated at about 55,000 tons, this rate of exploitation could rapidly decrease, because if it were maintained without new veins being discovered, the mines could be exhausted in the next 20 years or so. sentence.
The gold resources contained in the subsoil
Gold price in Australia mining is an extremely expensive industry, relying on technology and equipment that requires time and heavy investment to deploy. Not all gold deposits have been discovered, and many veins, which remain unexploited because technologies are insufficient or costs too high, certainly will be in a few decades, redrawing the map of the distribution of resources at as technologies evolve.
The main alloys containing gold
In the native state,
Gold price in Australia is a very malleable metal, which facilitates its use in goldsmithery. However, to ensure the strength of gold forged jewelry, it must be combined with other precious metals that will give it their hardness and prevent it from being deformed.
Until 4 January 1994, the date from which a law made it possible in France to produce alloys with only 58.5% gold (14 carats gold) and 37.5% (9 carats gold), The only alloy allowed by law was 18-carat gold, also called 750 thousandths because it comprises 75% gold and 25% other precious or semi-precious metals.
In the case of jewelery fashioned from an 18-carat alloy, systematically containing 75% gold (750 thousandths), various colors can be obtained:
So called gray gold an alloy of 75% gold and 25% palladium or 25% nickel.
Red gold contains 25% copper.
Green gold contains 25% silver.
The yellow gold contains about 12.5% silver and 12.5% copper.
The pink gold designation refers to an alloy containing 19% copper and 6% silver.
The white gold contains 19% silver and 6% copper.
Gold price in Australia designation refers to a shaped object with a minimum of 995 thousandths of gold, and a maximum of 5 thousandths of alloy. An ingot measuring 996 thousandths is thus legally considered to be made of fine gold.
Legal titles applied to gold
The main legal titles in force are:
Gold 999 thousandths, or 24 carats.
916 thousandths gold, or 22 carats.
Gold 833 thousandths, or 20 carats.
750 thousandths gold, or 18 carats.
Gold 585 thousandths, or 14 carats.
Gold 375 thousandths, or 9 carats.
It is forbidden to affix the words “gold alloy” for objects measuring 585 or 375 thousandths. This is only allowed for higher titles.