How is gold formed and where does it come from? | News | Aurica
How is gold formed and where does it come from?
Tuesday, December 10, 2024
By StoneX Bullion
Gold has been associated with wealth, power and beauty for centuries in all human civilizations, but how exactly did this precious metal form and where does it come from?
In this article, we look at the origins of gold in the cosmos, the geological processes that helped it form on Earth and where it is found. We also look at when gold was discovered, the possible sources of gold in the future and whether or not gold can be synthesized.
Where does gold come from?
The origin story of gold goes back to the earliest times in the solar system. To understand where it comes from, we have to go back to before our planet was formed....
The history of gold begins in the stars, with supernova explosions and neutron star collisions. These cosmic cataclysms involve explosions so extreme that they create heavy metals, including gold, and hurl them into space as part of the cosmic dust. Over billions of years, this dust, enriched with gold particles and other elements, formed new stars and planetary systems, including our solar system.
When the Earth formed about 4.6 billion years ago, the planet differentiated into layers. During this period, gold and other heavy elements sank into the Earth's core. However, not all of it arrived there and some remained in the Earth's mantle and crust, waiting to be discovered.
Although some of Earth's gold has been here since the formation of our planet, it is believed that a significant portion arrived via asteroids. This theory explains why so much gold is found near the Earth's surface. Either way, gold has traveled through the depths of space and time to reach our planet. But its journey does not end there: several geological processes are required to turn gold into the precious metal we treasure today.
How is gold made?
Cosmic phenomena and asteroids brought gold atoms to Earth, but millions of years of geological processes transformed these particles into gold deposits. These processes include hydrothermal activities, magmatic processes and various geological conditions deep in the Earth's crust. Let's take a look at how gold is formed.
Hydrothermal activities: one of the main ways gold is formed is through hydrothermal processes. Deep in the Earth, mineral-rich water can be heated by the action of surrounding rocks and magma. This fluid begins to move through fractures and porous rocks, transporting gold and other minerals. When the hydrothermal fluids cool, the gold dissolves and leaches out of solution to form gold-bearing veins, often found within quartz or other rocks.
Magmatic processes: Another way gold is formed is through magmatic processes. Gold is often found in small quantities within the earth's mantle. When magma forms through the partial melting of mantle rocks, it can carry gold and other dissolved metals. As the magma rises to the surface, it carries the gold with it. When the magma cools and solidifies, the gold oozes out and forms veins or deposits within the surrounding rocks.
Where is gold found? Gold is found in various places around the world and the environment, geography and type of gold deposit tend to be different depending on how the gold was formed. Gold deposits are classified into two main types: primary and secondary deposits.
Primary gold deposits: Primary gold deposits are those where the gold is found in its original geological environment, usually along the edge of tectonic plates or in regions with volcanic activity. These deposits are formed through magmatic or hydrothermal activity, as gold-rich fluids travel through cracks and fractures within a rock and cool, leaving behind deposits of gold and other metals. There are two different types of primary gold deposits:
Vein deposits: these form when gold-enriched hydrothermal fluids travel through fractures in rocks. When these fluids cool, they form veins of gold-bearing minerals, such as quartz. These veins accumulate significant amounts of gold over time and create valuable deposits.
Disseminated deposits: these are small gold particles scattered throughout the surrounding rock, rather than in concentrated veins. Disseminated deposits usually form with certain types of igneous rocks, where the gold is disseminated through sulfide minerals.
How are primary gold deposits mined?
1. Primary gold deposits are extracted using subway or open-pit mining techniques:
(a) Underground mining: involves digging shafts and tunnels to access gold-bearing veins deep in the Earth. The ore is extracted and then processed to separate the gold from the surrounding rock.
b) Open pit mining: in this case, the surface rock is mined to access the ore beneath. It is most suitable for disseminated deposits, where the gold is spread over a large volume of rock.
Exploring for and extracting primary gold deposits can be complicated, however, they tend to be the most valuable source of gold.
Secondary gold deposits
Secondary gold deposits, also known as placer deposits, form when primary gold deposits break down over time due to weathering, erosion and water. This releases the gold particles within and redistributes them to new locations. Because gold is heavy and does not corrode, it tends to accumulate along riverbeds, streams or sedimentary environments. Gold particles, gold nuggets or gold flakes, all eroded by the action of moving water, are found in these deposits.
How are secondary gold deposits mined?
Secondary gold deposits are extracted using surface mining techniques such as panning, dredging and sluicing:
(a) Washing: involves washing sediments in a pan to separate gold particles from other materials.
b) Sluicing: Here, water flows through a sluice gate to wash sediments and capture gold particles.
c) Dredging: This process collects sediments from river beds or the ocean floor and processes them to extract gold.
These methods are easier and less expensive than those used for primary gold deposits, although they do not offer the same abundance of gold.
Where does most of the world's gold come from?
Gold is found in regions that exhibit the geological processes necessary for its formation (i.e. extreme heat and pressure). Typically, these are regions with a history of tectonic or volcanic activity, or areas containing ancient geological formations with auriferous rocks. These environments provide ideal conditions for gold to form, deposit and concentrate.
Major gold producing countries in the world include:
Porcelain
Australia
Russia
Canada
South Africa.
China
When was gold discovered?
Gold is often considered the first metal discovered and used by humans. The earliest known evidence of human interaction with gold dates to around 4600 BC in Bulgaria, where gold artifacts have been found at the Varna Necropolis burial site.
By 2600 BC, the ancient Egyptians were mining gold in large quantities and revered the metal for its association with the gods and the afterlife. At about the same time, the Sumerians of Mesopotamia and the Indus Valley civilization also used gold to make jewelry and other artifacts.
Around 700 B.C., the ancient Greeks were already mining gold throughout the Mediterranean and Middle East. The Romans expanded these operations and used techniques such as hydraulic mining to extract gold from riverbeds. At that time, gold was already being used to mint coins.
During the 15th and 16th centuries, the Age of Exploration was marked by major gold discoveries in America, which led to an influx of gold into Europe. In more modern times, gold discoveries around the world ushered in the "gold rush eras," including the California Gold Rush in 1848, the Australian Gold Rush in the 1850s, and the discovery of gold in the Witwatersrand Basin in South Africa in 1886.
How much gold is there in the world?
According to the United States Geological Survey (USGS), about 244,000 metric tons of gold have been discovered on Earth to date. That equates to about 7.8 billion troy ounces. That may sound like a lot, but because of its density, if we melted all the gold down, it could fit inside a cube about 23 meters wide on each side.
Most of the gold discovered in the world comes from just three countries: China, Australia and South Africa. This gold is found in various forms, including gold jewelry (47%), investment bullion and gold coins (22%), central bank reserves (17%), industrial uses (8%) and other purposes (6%).
According to the World Gold Council, since gold is virtually indestructible, in theory almost all the gold mined so far is still accessible and potentially recyclable. Scientists also believe that there are still around one million tons of gold within the top kilometer of the Earth's surface, waiting to be mined.
Where might gold come from in the future?
Gold is generally considered to be a finite resource. What happens when the Earth's gold reserves run out? Below, we look at where gold could come from in the future, including asteroids, the Moon and perhaps even a laboratory.
Mining gold in space: The concept of mining gold in space is no longer limited to the realm of science fiction, but could become a viable reality. Scientists are already exploring gold mining technologies in space, and when it comes to gold, we could have two options: mining gold from asteroids and from the Moon.
Asteroid mining: Asteroids, especially those classified as M-type (metallic), are believed to contain significant amounts of gold, platinum and other precious metals. These space rocks are remnants of the early solar system and are often rich in metals that were never incorporated into planets.
Mining asteroids could provide an unlimited supply of gold, thus relieving pressure on Earth's natural resources. A now defunct company called Planetary Resources was already looking into the possibility of expanding Earth's natural resource base by developing the technologies needed for asteroid mining. More recently, a start-up company called AstroForge is also exploring the feasibility of asteroid mining. Stay tuned...
Lunar mining: Another potential source of gold (and other valuable minerals) is the humble Moon. While not as rich in metals as the asteroids, the lunar surface contains resources that could potentially be valuable. We are still exploring what exactly those resources are, but several missions are planned to find out, including NASA's Artemis program, which also seeks to establish a sustainable human presence on the Moon.
Future meteorite deposits: The future of gold could also come from meteorites...they transported gold to Earth before, so why not do it again?
Meteorites are the remains of asteroids and comets that survive their journey through the Earth's atmosphere. They are known to contain valuable metals, although most meteorites are small and do not contain commercially viable amounts of gold. That said, larger impacts in the future could bring significant amounts of the precious metal to Earth. While difficult to predict and control, this could potentially be another source of gold in the future.
Can gold be synthesized in a laboratory?
What if gold could be made in a laboratory? For centuries, alchemists have been trying to transform base metals into gold and, in theory, it is possible. There have even been cases where scientists have succeeded in creating miniscule amounts of gold in laboratories using nuclear reactors and particle accelerators. However, these methods only produced a miniscule amount of gold and at an extremely high price.
While it is possible to synthesize gold from a scientific point of view, the process is not viable for commercial or practical use due to its high cost, low yield and extreme complexity. As such, synthetic gold production is unlikely to replace traditional mining and extraction methods. For now, it appears that the Earth's natural gold reserves are the only way to obtain this precious metal.
