Incredible? No – it actually is possible. The total quantity of gold and other precious metals dissolved in sea water is really incredible. It has been estimated that we have mined over 5 billion troy ounces of gold since mining began about 6,000 years ago. By comparison, the concentration of gold in seawater is, according to scientific estimates, that the oceans contain somewhere in the region of 25 billion troy ounces, and that this quantity is increasing constantly as more gold comes out from the earth's mantle.
There are several ways in which this gold could be collected, and a few companies have trials underway. Distillation would be one method – basically distilling seawater and refining the residual. This is uneconomic as the energy required to boil off the water is feasible, although potentially a product of desalination plants with added stages. Beside gold, practically all naturally occurring elements are dissolved in sea water, to some degree.
There is now a more exciting and potentially economic solution – literally. In the regions of the ocean bottom where the earth's tectonic plates are separating (you may have heard of the Mid-Atlantic Ridge and continental drift for example), there are cracks in the ocean floor into which sea water penetrates. It is heated in the earth's mantle (these mid oceanic rises are made of hot rock) and minerals dissolve in it. The mineral-loaded water emerges through underwater fumaroles, and the minerals are deposited, which build chimney-shaped structures.
Scientists have discovered over three hundred previously unknown species surviving in this apparently inhospitable environment, where temperatures can reach over 200 degrees centigrade or more and water pressure is as much as three hundred times that at the surface. These species range from bacteria to limpets, shrimp and giant tube worms.
It is thought that bacteria (also known as extremophiles) play an important role in the anticipation of the minerals which build the chimneys – sulphur-oxidizing bacteria of the genera Beggiatoa, Thiothrix or Thiovulum may be involved in this process.
Some observers have suggested that it may be possible to genetically engineer these bacteria to extract gold and other precious or strategic elements and compounds from the sea. Bacteria have already been engineered to devour crude oil, so why not gold?
It will be the economics that drive this of course. Some mining companies are already developing bacteria to help with the further refining of low content gold ore waste produced from traditional gold extraction operations (bio-oxidation).
Recent difficulties in the world economy, and even talk of a return to the gold standard, may result in a continuing climb in gold prices (they have been steadily increasing for many years) – probably for at least ten years – and this will very likely Tilt the economic scales of gold extraction and refining towards even more marginal methods.