Many of the prospectors seeking to strike it rich during the California Gold Rush traveled thousands of miles by foot, wagon or horseback. But for us modern-day millionaire hopefuls, any old coastline just might do the trick.
That's because in 1872, British chemist Edward Sonstadt discovered scant traces of gold in seawater. At that point, scientists already knew about the silver, copper and lead hidden within the world’s oceans — but nothing yet as valuable as gold. Sonstadt suggested that large tanks could be used during high tide to trap and extract wealth from the seas (estimated to be about 65 milligrams of gold per ton of seawater).
Today, some experts argue that seawater extraction could become a more attractive alternative to current gold mining practices and future deep-sea gold mining — a scheme to collect the gold and other metals that shoot out of hydrothermal vents, often located more than a mile below the surface, and build up on the seafloor. Although mining in international waters is expected to begin in 2025, and the International Seabed Authority has so far issued more than 30 contracts for the exploration of deep-sea mineral deposits, experts argue that doing so will irreparably damage ocean ecosystems that are already struggling to combat climate change.
Unfortunately, Sonstadt's calculations were generous. A 1990 study published by MIT scientists instead found that there’s only about 1 gram of dissolved gold (worth around $63 today) for every 100 million tons of water in the Atlantic and Pacific Oceans. If you do the math, that’s at least a few hundred billion dollars floating around out there, depending on the estimated volume of the world’s oceans. At such low concentrations, however, it probably wouldn’t pay off to extract it with the technologies available to us today.
