The chemical element gold has a atomic number of 79 and is a bright orange-yellow metal. It is a transition metal, a group 11 element with an atomic symbol of Au. Because it is a metal with a higher atomic number than silver, it is a soft, malleable, and ductile metal. Its properties make it a desirable material in many applications, including jewelry and investment opportunities.
The concentration of gold in oceans varies, ranging from 50 femtomol per liter to 10-30 parts-per-quadrillion (pptv) and g/km3. However, samples from the central Pacific and south Atlantic have much higher concentrations. This is due to wind-blown dust and rivers, which can accumulate in the deep ocean. A concentration of 10 parts-per-quadrillion would correspond to about 15,000 tonnes of gold.
In addition to being valuable as a currency, gold is associated with great human achievements. It is often used to honor winners of graded competitions and athletic competitions. Various awards and statues are made of gold, including Oscar statues and British Academy Film Awards. These events are notable for their widespread usage and influence on the world. It also has a symbolic value. In fact, 75% of the world’s gold has been mined since the mid-19th century, and two-thirds of it was mined since the 1950s.
Gold occurs naturally in the earth’s crust. It is usually found in very small particles deposited with quartz and sulfide minerals. Some of these gold particles end up as free flakes or nuggets. This type of gold ends up in placer deposits. The free gold is richer near the surface of gold-bearing veins. It can be welded together by water action. These minerals are known as alluvial deposits.
Gold in the earth’s crust and mantle may have come from space. A 2011 Nature paper found that 20 billion tons of gold were brought to Earth by meteors. The metal was part of a precious metal-rich space rock, and was most likely deposited in the earth’s crust by an ancient collision of a star. A 2013 Astrophysical Journal Letters study concluded that gold in the Earth’s mantle and crust could have come from the same source.
Gold is found in rock from the Precambrian period on. It occurs as a free metal or as a metal solid solution with silver. Most gold-silver alloys contain a silver content of eight to ten percent. Natural, white gold is elemental and contains more than 20% silver. It is also called electrum, which is white gold. The amount of copper found in the metal determines its color. Further, natural, native, or synthetic gold is rare in nature.
A common source of gold is found in hydrothermal veins. This mineral is found in some sulfide deposits. It is not oxidized and does not tarnish. Its color is unique to each mineral. It is the most precious metal in the world, and is valued by everyone, from royalty to jewelry. A recent study showed that more than half of all gold is recycled. But there are still many cases of gold in plastic bags and other products.