How To Extract Gold From Seawater

Incredible? No - it actually is possible. The total quantity of gold and precious metals dissolved in sea water is really unbelievable. Estimates say that we have mined more than 165,000 tons of gold since mining first 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 nearly a million tons, and that this quantity is increasing constantly as more gold leaches out from the earth's mantle.

There are several ways in which this gold could be collected, and a number of companies have trials underway. Distillation would be one method - basically boiling seawater and refining the solids left over. This is not economic as the energy required to distil the water is considerable, though potentially a product of desalination plants with added stages. Besides gold, practically all naturally occurring elements are dissolved in sea water, to some degree.

There is now a potentially economic solution - literally. In regions of the sea floor where the earth's tectonic plates are separating (you may have heard of the Mid-Atlantic Ridge and continental drift for example), there are fissures in the sea bottom into which sea water flows. It is heated in the earth's crust (these mid oceanic ridges are made of of hot soft rock) and minerals dissolve in it. The mineral-rich water emerges through underwater fumaroles, and the minerals are deposited, which build chimney shaped structures or other forms of deposit.

Researchers have found more than three hundred new species living in this very aggressive 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.

Biologists believe that bacteria (also known as extremophiles) play a significant role in the precipitation of the mineral deposits which build the chimneys - sulphur-oxidizing bacteria genera such as Thiothrix or Thiovulum may be involved in this process.

Some researchers have suggested that it may be possible to genetically engineer these or similar 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 tailings produced from traditional gold extraction operations (bio-oxidation).

Recent difficulties in the world economy, and even talk of a return to the gold standard, are almost certain to lead to a continuing increase in gold prices (still increasing sharply) - probably for at least another 10 years - and this will inevitably tip the economic scales of gold mining and refining towards more marginal methods.