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Dr. Sten Odenwald is an Astronomer at the National Institute of Aerospace.
The first documented use of gold by humans was found in the jewelery recovered from the Varna Necropolis in Bulgaria and dated to about 6,500 years ago. Since then, enough gold has been mined from Earth’s crust to form a cube 60 feet on a side.
Gold is one of the 100-odd basic elements in the universe. Number 79 in the element list, a cubic meter of it weighs 19 metric tons. Your ‘weight in gold’ would be worth over $2 million! How much gold is there?
The most common ingredient to Earth’s crust is silicon. It makes up beach sand, granite, sandstone and the actually the entire lithosphere. By comparison, you have to sift through about 250 metric tons of this stuff to come up with a measly 1 gram (5 carats) of gold. This kind of a gold mine would be rated at 0.004 g/ton. Generally, industrial mining is only economically feasible if the rating is about 1gram/ton or higher! The best mines produce gold at ratios of 5 gm/ton or more when a rich ore vein is available.
How about sea water? For every 250 million liters of water you will get about 1 gram of gold. This works out to about 1 gram for every 255,000 tons of water or a ratio of 0.000004 g/ton. This of course will be mixed with all kinds of other sediments in solution too, like 34,000 g/ton of sodium, chloride and other ions. So mining for gold in the ocean is not just a matter of evaporating away the water!
Across the universe, gold is pretty rare. For the sun, the largest reservoir of matter (mostly hydrogen) in our solar system, we can detect the light from gold atoms and figure out their abundance. The answer is that, for every trillion atoms of hydrogen, you get about 10 atoms of gold. So this works out to 4 trillion trillion grams of gold in the entire sun, or a miner’s ratio of 0.002 g/ton. That’s even worse than what you find in Earth’s crust, but instead of mining granite and silicates, you would have to sift through million-degree hydrogen plasma!
Ok. How about the moon? Astronauts brought back hundreds of pounds of rock from the lunar surface that were carefully analyzed (trust me on this). The Apollo 11 rock samples had about 0.04 parts per billion of gold atoms, in rocks that were mostly like Earth crust. This works out to about 0.0003 g/ton. That’s worse than the sun but not as bad a sea water! The recovery cost of 840 pounds of moon rocks by the Apollo program was about $250,000 per gram. Gold is worth only $39/gram.
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