1. Gold in Seawater
Scientists have known for more than a century that seawater contains dissolved gold, although the concentration is extraordinarily small. The U.S. Geological Survey reported seawater values averaging approximately 0.05 parts per billion in studies available at the time.[1] Because the oceans contain an immense volume of water, the total quantity of dissolved gold is significant, but concentration rather than quantity determines whether a resource can be mined economically. This distinction explains why numerous attempts to recover gold from seawater have failed. The gold exists, but it is dispersed through such a large volume of water that extraction costs greatly exceed the value of the metal recovered.
2. Gold in Freshwater
Gold also occurs in rivers, lakes, springs, and groundwater systems. Water moving through mineralized rocks can dissolve trace amounts of gold and transport it downstream.[1] Although concentrations are generally low, water plays a major role in the natural gold cycle because hydrothermal fluids and groundwater systems help move gold through the Earth’s crust. Many gold deposits ultimately owe their existence to the transport of dissolved gold by water followed by precipitation when temperature, pressure, or chemistry changes.
3. Gold in Plants
Researchers have detected measurable amounts of gold in numerous plant species growing above gold-bearing rocks and soils.[1] Plants absorb water and dissolved substances through their root systems, and trace amounts of gold may be absorbed along with other elements. These observations led to geobotanical prospecting techniques in which vegetation is analyzed for unusual concentrations of metals that may indicate buried mineral deposits. Although plants can contain measurable gold, the concentrations remain far too low for practical recovery.
4. Gold in Marine Animals
One of the most interesting findings in the U.S. Geological Survey compilation involved gold concentrations in animals. Jones reported values ranging from 0.0012 parts per billion to 430 parts per billion on a dry-weight basis.[1] Using the report’s average seawater value of 0.05 parts per billion, the highest reported animal concentration would be approximately 8,600 times greater than the surrounding seawater concentration.[1] This does not mean marine animals contain large amounts of gold. It means biological systems are capable of concentrating trace elements relative to their environment.
5. Bioaccumulation of Gold
Bioaccumulation occurs when organisms absorb substances from their environment faster than they eliminate them.[2] The process is well known for metals such as mercury, copper, selenium, zinc, and silver, and evidence indicates that gold can also be concentrated within biological tissues. The key concept is that concentration factors can become very large even when the total amount of metal remains microscopic. This distinction between concentration and quantity is one of the most important concepts shared by biology and economic geology.
6. Microorganisms and Gold
Modern research has shown that microorganisms may participate in the cycling of gold within natural environments.[3] Scientists have documented bacteria associated with gold-bearing environments and naturally occurring gold particles, and some species appear capable of interacting with dissolved gold compounds and contributing to the formation of microscopic metallic gold particles.[3] These discoveries have expanded scientific understanding of how gold moves through soils, sediments, groundwater, and weathering systems, although microorganisms are not considered the primary mechanism responsible for forming major gold deposits.
7. Why We Do Not Mine Gold From Organisms
The observation that plants and animals contain measurable gold naturally raises the question of whether they could become a source of commercial production. The answer is generally no. While concentration factors may appear impressive, the actual quantities involved remain extremely small. A marine organism may contain thousands of times more gold than seawater on a concentration basis while still containing only microscopic amounts of metal. Economic mining depends on total recoverable gold rather than concentration factors alone.
8. Conclusion
Gold occurs throughout the natural world, including seawater, freshwater, plants, animals, and microorganisms. Scientific studies show that biological systems can concentrate gold to levels far above those found in surrounding waters, yet the total quantities remain extremely small. The occurrence of gold in living organisms provides a useful reminder that nature constantly concentrates metals through geological and biological processes. The critical question is not whether gold exists, but whether enough gold has been concentrated in one location to become an economic resource. That distinction ultimately separates trace occurrences from the deposits that become mines.
Related Reading
Why Gold Forms, Moves, and Concentrates
The Complete Guide to Gold Geology and Gold Deposit Types
The Complete Guide to Gold Prospecting Clues: Minerals, Alteration, Veins, and Host Rocks
References
[1] Jones, Robert S. Gold Content of Water, Plants, and Animals. U.S. Geological Survey Circular 625.
[2] Eisler, Ronald. Trace Metal Concentrations in Marine Organisms. U.S. Fish and Wildlife Service.
[3] Reith, F., Fairbrother, L., Nolze, G., et al. Nanoparticle Factories: Biofilms Hold the Key to Gold Dispersion and Nugget Formation. Proceedings of the National Academy of Sciences.