On the BBC News programme this morning (http://news.bbc.co.uk/1/hi/programmes/breakfast) I noted mention that there is thought to be enough recoverable gold to fill "three Olympic sized swimming pools"(OSSP) and enough platinum to occupy one such volume "up to your ankles". According to FINA (Fédération Internationale de Natation), the body recognised by the International Olympic Committee for administering international competition in the aquatic sports, an OSSP has at least a length of 50 m, a width of 25 m and a depth of 2 m, making a volume of 2,500 m^3.
Now, this does place a tangibly illustrative physical dimension on how much of these metals might be available.
In the case of gold, we may deduce that there are 3 x 2,500 m^3 x 19.3 t/m^3 = 144,750 tonnes recoverable.
In the case of platinum, the sum may run something like 2,500 m^3 x 21.45 t/m^3 x ("up to my ankles", say 4 inches, or 0.1 m/2 m) = 2681.25 tonnes recoverable.
The value for platinum shocks me, as I had heard there were maybe 36,000 tonnes recoverable, but I have found an interesting analysis (http://www.platinum.matthey.com/production/resources-in-south-africa/) which places the issues of resources and reserves into perspective. This report concludes there are "estimated proven and probable reserves of platinum at 203.3 million troy ounces, (6,323 tonnes)"... plus... " In addition to these reserves, inferred resources were estimated at 939 million troy ounces (29,206 tonnes) of platinum." So, taken together, this is about the amount I had understood existed.
However, the bulk of this is likely to be got at far reduced EROEI, and greater difficulty/cost, though a more valuable product will urge more assiduous efforts to produce it. If one does the sum in reverse, i.e. 2m x 6,363 t/(2,500 x 21.45) = 0.24 m, I deduce that the OSSP would be filled with platinum to about nine and a half inches up my leg, which is about half way up my calf, and well above my ankles.
But how much gold is there? According to the USGS (http://oilprice.com/Metals/Gold/Recoverable-Gold-Resources-to-Run-Out-in-20-Years.html) there are 51,000 tonnes, which is more like one OSSP, rather than three. I have seen estimates that maybe up to half a million tonnes of gold might be recovered, but the quality of gold ore is falling. In 1960, one tonne of gold ore yielded 2.86 grams of gold, but by 2000 only 1.37 grams of gold were recovered per tonne. The most recent gold ore discoveries are yielding less than one gram per tonne. Thus, the situation is like oil, that most of the easily-had stuff has been had, and more energy and resources (reflected in the falling EROEI) must be expended to recover and process a poorer quality material.
In making Jewellery, the highly resistant nature of Gold and Platinum symbolises eternity, e.g. in wedding-rings. However, gold and the platinum group metals (PGM) have many important practical uses. Gold finds increasing application in the circuitry of computers, while platinum, rhodium, palladium and rhenium provide catalysts, e.g. in catalytic converters, fuel-cells, and the production of synthetic fertilizers. If the supply of these metals will fail demand for them, many central and projected technologies for communications, transport and food production must be re-thought.