One cubic mile of seawater contains about 25 tons of dissolved gold.
The Ocean Holds 25 Tons of Gold Per Cubic Mile
Every wave that crashes on the shore carries traces of treasure. The world's oceans contain an estimated 20 million tons of dissolved gold, with each cubic mile of seawater holding approximately 25 tons of the precious metal. That's enough gold in a single cubic mile to be worth over $1.5 billion at current prices.
So why aren't we all ocean mining billionaires?
The Cruelest Math Problem
Here's the catch: that 25 tons is spread across 1.1 trillion gallons of water. The concentration works out to roughly 13 parts per trillion—or about one gram of gold for every 100 million grams of seawater. To put that in perspective, you'd need to process about 250 million gallons of seawater just to recover a single ounce of gold.
The energy costs alone would bankrupt anyone foolish enough to try.
People Have Definitely Tried
The dream of ocean gold extraction has lured inventors and schemers for over a century:
- Fritz Haber, the Nobel Prize-winning chemist, spent years in the 1920s trying to extract gold from seawater to pay off Germany's WWI debts. He failed spectacularly.
- Prescott Jernegan ran an 1890s scam convincing investors he'd invented a "gold accumulator" that extracted gold from the sea. He fled to Europe with $350,000.
- Dozens of patents have been filed for seawater gold extraction. None have proven economically viable.
Where Does the Gold Come From?
The ocean's gold comes from two main sources. Rivers continuously wash gold particles from rocks and soil into the sea, a process that's been happening for billions of years. Meanwhile, hydrothermal vents on the ocean floor spew mineral-rich water that includes gold dissolved from the Earth's crust.
The concentration has remained relatively stable because gold is chemically inert—it doesn't react with seawater, so it just stays dissolved indefinitely.
The Real Ocean Gold Rush
While dissolved gold remains forever out of reach, seafloor mining is becoming a reality. Mineral-rich nodules and hydrothermal deposits on the ocean floor contain gold in much higher concentrations, along with copper, manganese, and rare earth elements.
Several companies are developing deep-sea mining operations, though environmental concerns about disrupting fragile ocean ecosystems have slowed progress.
The ocean guards its treasure well. That 20 million tons of gold will likely remain exactly where it is—tantalizing humanity with wealth we can calculate but never claim.