Gold is a precious metal used in many ways for thousands of years. Gold is renowned for its lustrous beauty and enduring value, and it occupies a unique place in the vast tapestry of Earth’s geological history. You can find gold as beautiful jewelry indicating power and prestige, a store of wealth in bank vaults behind thick steel doors, or an efficient conductor in electronic devices. The uses and applications of the metal are ever-changing, and gold has captivated civilizations for millennia. But how is gold formed, and where does gold come from? To answer that question, we must look to the stars.
Where Does Gold Come From?
To learn about the origin of gold, we must first turn our gaze to the cosmos. Gold is not native to our planet alone; it is a cosmic traveler that finds its roots in the cataclysmic events occurring in the far reaches of the universe. So, how is gold formed, and where does gold come from? The birth of gold is linked to the dramatic demise of massive stars in explosive supernovae and neutron star collisions.
When a star exhausts its nuclear fuel or collides with another star, it undergoes a stellar explosion, scattering elements forged in its core across the cosmos. These elements include heavy elements like gold, which form during the intense heat and pressure within the star. The released debris, now enriched with these precious metals, disperses into space, creating vast interstellar clouds. These interstellar clouds are the material that eventually forms into other stars and planets, such as Earth.
How is Gold Formed by Supernovae?
A star’s shine is created by nuclear fusion. Pulled together by gravity, hydrogen atoms slam together to form helium atoms, which release enormous amounts of energy in the form of heat and light. Eventually, the hydrogen in the star’s core runs out, and gravity causes the star to collapse. What happens next depends on the star’s mass, but gold is formed when the collapse creates a massive shockwave.
During the explosion, a tremendous amount of energy creates heavy elements through the rapid neutron-capture process. The process occurs when one or more heavy seed nuclei rapidly capture the available neutrons faster than radioactive decay can begin. The heavy elements created, including gold, are transported through space to their destination or become the beginning formations of new stars or planetary systems.
How is Gold Formed by Neutron Star Collisions?
The collision of neutron stars can also cause the rapid neutron-capture or r-process. Throughout the galaxy, some neutron stars are stuck in a binary star system, orbiting each other. Over time, they get closer and closer before eventually merging. The mass amount of energy produced during a collision creates the same conditions as a supernova, allowing heavy elements such as gold to be formed. Scientists witnessed a gravitational wave caused by a neutron star collision in 2017. They could detect heavy elements upwards of 16,000 times the mass of the Earth. These detections included gold formations amounting to 3-10 times the mass of Earth.
Gold on Earth
Gold is a well-known precious metal labeled as Au on the periodic table of elements. With an atomic number of 79, it has been an essential part of human history since 3000 BCE. The journey of gold to Earth is far from straightforward. Billions of years ago, our planet formed from the remnants of a protoplanetary disk, a swirling mass of gas and dust surrounding the young Sun. The early Earth was a seething cauldron of molten rock devoid of the metals we prize today.
Heavy elements, including gold, began to migrate towards the core through various geological processes as our planet cooled over eons. One key player in this cosmic ballet is the element iron. Gold has a natural affinity for iron, and during the differentiation of the Earth’s layers, it selectively combined with iron to sink into the core. Most of the gold within our planet is deep within the core, inaccessible to us due to the extreme depth and heat of Earth’s core. So, where does the gold we use come from if we cannot reach most of it?
Transported through Space
While a significant amount of gold resides deep within the Earth’s core, what we mine today is often closer to the Earth’s surface. Scientists generally agree that the gold in the planet’s crust came from the same place as the gold in Earth’s core: space. The consensus is that meteors transported gold and deposited it throughout Earth’s crust during a bombardment. Through hydrothermal processes and forces of erosion, these gold deposits became discoverable.
Hydrothermal Processes
Hydrothermal processes play a crucial role in bringing gold closer to accessible depths. These processes involve the movement of hot fluids through the Earth’s crust, dissolving and transporting minerals, including gold, along the way. These fluids could be molten lava in a volcanic area.
When these mineral-laden fluids encounter cooler conditions or suitable host rocks, they deposit the dissolved gold. This can lead to gold deposits or veins forming in various geological settings, such as quartz veins, which are common hosts for gold. The intricate dance of temperature, pressure, and chemical reactions orchestrates the creation of gold deposits that await discovery.
Nature’s Gold Pan
In addition to hydrothermal processes, gold can be transported and deposited by the forces of erosion and weathering. Rivers, streams, and other water bodies have been nature’s gold pans for centuries, carrying minute gold particles from their sources to new locations.
As water courses through gold-rich areas, it wears away rocks and releases the gold, which, being dense, settles in riverbeds as placer deposits. The famous Klondike Gold Rush of the late 19th century in the Yukon, Canada, is a testament to the allure of placer deposits, where prospectors braved harsh conditions in pursuit of elusive gold nuggets.
Witwatersrand Basin: The Gold Vault of Earth
A journey to the Witwatersrand Basin in South Africa is for those intrigued by the most prominent and prolific gold deposit ever discovered. This geological wonder, stretching for about 300 kilometers, is a gold treasure trove that has yielded a significant portion of the world’s gold. The amount extracted from the Witwatersrand Basin is estimated at over 40,000 tons of gold.
The Witwatersrand Basin’s gold deposits were formed around 2.8 billion years ago through hydrothermal and sedimentary processes. Layers of sediment, rich in gold, accumulated over time and were later compressed into the hard rock formations we mine today. This extraordinary basin stands as a testament to the Earth’s geological history and the intricate processes that give rise to gold.
Modern Gold Mining
Today, the quest for gold continues, albeit with a sophistication unimaginable to our forebears. Modern gold mining involves a delicate balance between technology, environmental stewardship, and sustainable practices. Miners use advanced techniques, such as gravity separation and cyanide leaching, to extract gold from its ores. We have made technological advances that allow us to operate machines in the depths of a mine from the surface of the Earth.
However, we must consider the environmental impact of gold mining. Responsible mining practices, community engagement, and ecological conservation are integral to mitigating the environmental footprint of this precious metal extraction. Striking a balance between the economic benefits of gold and preserving our planet’s delicate ecosystems is a continuous challenge for the mining industry. Today, mines such as the Reefton Mine in New Zealand actively rebuild the natural landscape after the gold runs out.
Precious Legacy from the Cosmos
The story of gold spans billions of years, traversing the vastness of space and the depths of our planet. From the fiery furnaces of long-gone stars to the intricate dance of geological processes on Earth, gold’s journey is a testament to the cosmic alchemy that shapes our world.
As we continue to marvel at the brilliance of gold in our jewelry, coins, and investments, let us remember its cosmic origins and the geological processes that bring it within our reach. The allure of gold is not just in its monetary value but in the profound connection it shares with the universe and the intricate workings of our planet.
