Modern Day Alchemy
Iceland is a Geological Wonderland. Photo by Ben Smith
by Benjamin D. Smith
About Ben Smith: Ben is a geologist pursuing a Master of Science Degree in Sustainable Energy at Reykjavik University in Iceland
The advancement of civilizations throughout history has greatly depended upon their ability to extract metals from the earth. Mining required harsh labor using crude tools with low productivity. Because of these overwhelming hardships, alchemy was pursued in the medieval ages where they erroneously believed that they could find a way to transform less valuable metals into gold or silver. With our modern understanding of chemistry, we know that pursuit was impossible; however, we now understand metal forming processes and current technologies enable us to extract metals from ore that might seem to be simple rock. As seen in the picture below the rock does not have obvious gold or silver exposed, but this is some of the highest-grade ore in the world (found in Grass Valley, Nevada).
Rock altered by epithermal systems that contains high amounts of gold
While we cannot use alchemy to change the fundamental elements of metals, we now have the ability to find gold in places that seem to be void of it. Metal deposits are being formed now by active geothermal systems. Much of metal being mined today and that has been mined throughout history was formed by geothermal systems that are now inactive. Through research and development we are gaining a better understanding of how these metals are transported to enable us to extract the metals out of geothermal fluids before the metals are deposited. This is a “game changer” as we seek ways to satisfy ever growing international appetites for metals ranging from gold to lithium.
Metals and Minerals Within Active Geothermal Systems
When magma starts its journey from deep within the Earth the concentration of gold within it at the mantle is relatively small; however, as the magma rises to the surface it cools and light minerals, such as quartz and feldspars, solidify out of the molten solution leaving the magma with higher concentrations of various metals and minerals. This process continues through various stages over long periods of time. As the melt comes closer to the surface, aqueous transport becomes more important. Faults or cracks near the surface then become important as this is where the fluid tends to travel.
Gold Mining From Epithermal Deposits
Current day mining of gold is related to the process stated above, however, it is associated with ancient, inactive geothermal systems. Over long periods of time the gold accumulates and creates economic grade ore deposits. One of the richest gold ore deposits is from an epithermal deposit found in Nevada. This epithermal system is unique however as the epithermal fluid is in contact with carbonate rocks creating a Carlin type deposit. These systems have very high grades of gold, making them some of the most profitable gold mines in the world.
How Gold is Transported by and Extracted From Water
Much like how sugar is dissolved in water, gold can be in solution with water. Even in the ocean there are trace amounts of gold. The process of carrying gold is complicated as it requires the correct chemistry, pH, and temperature for high amounts to be carried. In a liquid solution, gold is typically carried in hydrogen sulfide chemicals, such as, Au(HS)2-. The gold is in solution with the fluid, however, when the fluid changes chemistry or boils, the gold is dropped out of solution.
Can Metals be Extracted from Geothermal Fluids?
It is possible to extract gold and other metals out of geothermal fluids. While additional research and development is needed, some companies are already working to extract metals from geothermal fluids. Lithium extraction shows much promise in California due to the growing demand for lithium batteries. The Salton Sea Geothermal Field has the potential for 600,000 tons of lithium extracted per year according to a March 2020 CEC report titled “Selective Recovery of Lithium from Geothermal Brines”.
With a growing worldwide demand for renewable energy and metals, metal extraction could prove to be a major factor in the economics of geothermal energy production.
This is a “game-changer”
Contact: bendsmith917@gmail.com
