What Is The Origin Of Gold?

Yellow like Sun and Moon, revered for its aesthetic and metallurgical properties forthousands of years, gold is still today one of the most sought-after precious metals.There’s no question about it — for better or for worse, gold has played a unique rolefor humanity. Today we will explore the fascinating historyof a metal that, like and perhaps more than iron, has influenced the destiny of all civilizationsthat have followed one another on Earth in recent millennia, trying to answer the questionthat most likely you will have asked yourself from time to time: what is the origin of gold?Why do we find it on our planet?From the Neolithic of the Middle East to the Bulgarian Necropolis in the 4th millennium,from the Egyptian pharaohs to the Spanish conquistadors, the allure of gold – itspowerful effect on us – has been consistent and unmistakable. In fact, the Egyptians calledgold “the breath of God”. And it’s not just the ancients that held gold in high esteem.What myths made gold such a prized commodity and what factual properties still supportit as a precious metal to this very day? First and foremost, what makes a preciousmetal is its rarity. Rarer than silver or copper, two other metals mined since antiquity,its value was proportionately larger. Second, gold has fantastic properties. It does nottarnish, it’s very easy to work, can be drawn into wire, hammered into thin sheets,it alloys with many other metals, can be melted and cast into highly detailed shapes, hasa wonderful color and a brilliant luster. All of these properties could be harnessedsince ancient times, like today, just by heating gold nuggets at high temperatures and usingsimple tools like hammers or molds. In short, gold is very memorable, so it shouldn’tcome as a surprise that its main use is in jewelry.Since time immemorial the noble metal’s resplendent luster allows it to be designedinto the world’s most coveted and exquisite jewelry — fit for queens or kings. Today,most of the gold that is newly mined or recycled is used in the manufacture of jewelry. About78% of the gold that’s available, as opposed to stored, each year is used for this purpose.Because gold is highly valued and in very limited supply it has long been used as amedium of exchange or money. The first known use of gold in transactions dates back over6000 years. The first gold coins were minted under theorder of King Croesus of Lydia (a region of present-day Turkey) in about 560 BC. Goldcoins were commonly used in transactions up through the early 1900s when paper currencybecame a more common form of exchange. The United States once used a “gold standard”and maintained a stockpile of gold to back every dollar in circulation. Under this goldstandard, any person could present paper currency to the government and demand in exchange anequal value of gold. Possibly gold’s greatest use to mankinddidn’t become evident until early last century when its fantastic electrical conductivityproperties came to light. Solid state electronic devices use very low voltages and currentswhich are easily interrupted by corrosion or tarnish at the contact points. Gold isa highly efficient conductor that can carry these tiny currents and remain free of corrosion,which is why electronics made using gold are highly reliable. A small amount of gold isused in almost every sophisticated electronic device. This includes cell phones, calculators,personal digital assistants, global positioning system units, and other small electronic devices.But the gold is able to amaze us with a bunch of other strange features…So, before trying to explain its origin, here are some curiosities. Enjoy them!Gold is the only metal that is yellow or “golden.” Other metals may develop a yellowish color,but only after they have oxidized or reacted with other chemicals.The chemical symbol for gold is Au, from the Latin word aurum, meaning “shining dawn”and from Aurora, the Roman goddess of the dawn.Gold is a noble metal. It is relatively unreactive and resists degradation by air, moisture,or acidic conditions. While acids dissolve most metals, a special mixture of acids calledaqua regia is used to dissolve gold. The atomic number of gold is 79, which meansthere are 79 protons in the nucleus of every atom of gold.The melting point of gold is 1,064°C Gold is extremely ductile. One ounce of goldcan be stretched to a length of 8 km; the resulting wire would be just five micronswide. Malleability is a measure of how easily amaterial can be hammered into thin sheets. Gold is the most malleable element. One ounceof pure gold (28,35 grams) could be hammered into a single sheet of nine square meters.A sheet of gold can be made thin enough to be transparent.Gold is one of the densest metals found on Earth, a cubic meter of gold weighs 19,300kilograms, far heavier than lead (11340 kg/m³) and not far off the densest metal, Osmium(22650 kg/m³). It is estimated that 142,000 tons of goldhave been mined throughout history. Over 90 percent of the world’s gold hasbeen mined since the California Gold Rush. The coffin found in Tutankhamen’s tomb containedaround 1.5 tonnes of gold. The average human body contains 0.2 mg ofgold. Gold ranks 75th in order of abundance of theelements in the Earth’s crust. Fort Knox holds 4,600 tonnes of gold.Today gold price: 57.22 dollars per gram The visors that protected Apollo 11 astronautsduring the first Moon walk, was gold-coated!It’s cool, isn’t it? But at this point, it is time to answer thelast question: when was the gold we are finding in the earth’s crust formed and where didit come from? Has it always been there? Or has it not?The topic is really thorny and even today has aspects not well understood. What we knowexactly is this: gold, like all other heavy elements existing in nature, can be formedonly in thermonuclear reactions of extraordinary power. And in nature, there is only one placecapable of this: the atomic furnace inside the stars.Could this be the origin of gold? Maybe… let’s try to understand it by retracing thewhole process of the formation of a star. All the stars start life largely composedof immense balls of compressed gas, mainly hydrogen, the first element produced afterthe ‘Big Bang’. Clouds of stellar hydrogen condense to forma swirling mass and the inward pressure is held in check by the outward pressure of thecompressed gas. The pressure and friction causes incredibleheat, resulting in a nuclear reaction at the center of the mass. Through a complex seriesof reactions, the hydrogen ignites and a star is born. Over billions of years, as the hydrogenis used up, outward pressure falls enough to allow gravity to squeeze the central coreeven tighter, causing greater pressure and temperature. At around one billion degrees,helium atoms are forged. As this element is devoured in the nuclearfurnace, the core continues to contract and increase internal temperatures until the heliumnuclei fuse to form carbon atoms. The process continues until further fusionreactions lead to oxygen, neon, and other elements materializing. By now the densityof the core is around 50 tonnes per cubic centimeter, compared to the Earth’s averagedensity of 5.5 grams per cubic centimeter. With a temperature of around two billion degrees,neon fuels a fusion reaction to form silicon – a major component of Earth. As each newelement is consumed, so the energy return steadily declines and the star changes, notevery ten thousand years or even every year, but first on a monthly, then daily, and finallyan hourly basis. The last stage is reached when the nuclearreaction produces an iron core – a more stable element without the ability to burn. The coreby now is typically 200 km across and very dense – it’s estimated that a teaspoonwill comprise around a trillion tonnes of matter – six thousand teaspoonfuls (or 30liters) would weigh as much as the entire mass of Earth.The star, with little nuclear energy remaining to support its own weight, contracts so forcefullyunder gravity that even atoms are overcome. The trillions and trillions of tonnes of materialsurrounding the core rushes inwards at tens of thousands of kilometers an hour, collidingwith the now solid core. The resulting shock wave, like nothing seenon Earth, travels outwards and is accompanied by a burst of neutrinos formed in the dyingmoments. The combined energy of the shockwave and neutrinos transform the star’s outerlayers into an intense stellar furnace. It is in this environment that heavy elementsbeyond iron are forged in a mad scramble of hyperactive atoms – then the star literallydisintegrates in the form of a supernova. Iron atoms, along with every other element,are blasted into space in a nuclear holocaust beyond anything imaginable.The star will shine with the intensity of ten billion of our Suns – at least for a fewdays. Fading within weeks, all that remains of thestar is a huge cloud of gas and dust containing the new elements.From this cloud, which in astronomy is called “nebula”, will condense in turn other stars,called “second generation stars”, which will incorporate and recycle all the new elementsbequeathed by the stars that have preceded them.But – be careful – among the heavy elements in the nebula there will be no trace of gold!At most, we will find iron! Until a decade ago it was believed insteadthat any star massive enough, at the end of its existence as a supernova would be ableto form elements even heavier than iron, such as gold, but soon it was realized that tosucceed would require energy much greater than that developed by a normal supernovaevent … And on August 17, 2017, astronomers had proofof their theory! Scientists, in fact, have for the first timeseen the collision of two neutron stars in the galaxy NGC 4993, located nearly 130 millionlight years from Earth. But the merger of two neutron stars is morethan fireworks. It’s a factory. Using infrared telescopes, astronomers studiedthe spectra – the chemical composition of cosmic objects – of the collision and foundthat the plume ejected by the merger contained a host of newly formed heavy chemical elements,including gold, silver, platinum, and others. Scientists estimate the amount of cosmic blingtotals about 10,000 Earth-masses of heavy elements!The discovery seemed to confirm that neutron star mergers were responsible for the productionof most of the heavy elements found in the universe.But certainties, even in astronomy last the space of a morning … and new observationsalready suggest that the number of possible collisions between neutron stars has beengreatly overestimated and that it is, therefore, necessary to assume cosmic phenomena evenmore energetic to justify the presence in the universe of so much gold.Whatever the cosmic origin of gold, to fully answer the initial question we still haveto explain its presence on our planet. It is true that it would be enough to say(as we have already done) that our solar system, Sun, planets, and everything else, was formedfrom dust rich in heavy elements left as an inheritance from stars of previous generations…However, there is a problem. In fact, as you already know, our planet wasformed about 4.5 billion years ago through a process of accretion that lasted millionsof years, made by attracting dust and planetesimals that met in its orbit around the Sun. Theenergy released by this incessant supply of matter then began to produce heat, so muchto reduce the young Earth in an agglomeration of molten rock, homogeneous and undifferentiated.The high temperatures, also fed by the natural radioactivity of the elements present, reachedand exceeded 1500 degrees centigrade, and this state of fluidity led the heavier elements,such as iron, nickel, and gold, to slowly sink towards the nucleus, separating fromlighter materials, which were pushed to the outer layers.So, if 4.5 billion years ago heavy elements left the earth’s crust to form the metalliccore of our planet, how come iron, nickel, and gold are still in abundance in mines aroundthe world? The answer is very simple.After the Earth’s crust cooled, solidifying, there was a period, from 4.2 to 3.8 billionyears ago, in which the meteorite bombardment resumed with great intensity, During thisinterval, a disproportionately large number of asteroids are theorized to have collidedwith the early terrestrial planets in the inner Solar System, including Mercury, Venus,Earth, and Mars. And it was the “Late Heavy Bombardment”, as it was then called, thatbrought back to the Earth’s surface most of those minerals that our planet had lost earlier!In short, we are telling you that all the gold we know… from what we wear to whatwe use in computers, from the funeral mask of the sarcophagus of Tutankhamen to the ingotslocked up in Fort Knox…In short, all the gold in this world, is something that comesfrom the stars, and from asteroids that devastated the Earth four billion years ago.الإنجليزية

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