posted on Jul, 15 2004 @ 02:27 AM
(C-type) asteroids are the best choice because they have everything needed to sustain an industrial economy. I claim you cannot harvest just one
asteroid. C-type does have hydrated minerals that can be baked at 1,000°C to get water out, and may have ice in the core. Water can be made into
LOX/LH2 rocket fuel. However, industrial metals are relatively scarce and in the form of oxide minerals. Those minerals would have to be smelted.
However, an iron asteroid is called M-type because it's solid metal. It is composed of iron/nickel alloy and may have mineral inclusions of up to
30%. If the inclusions are more than 30% it's no longer classified as iron, instead it's called stony-iron. Iron can be more than 90%, but on
average is 88% of the metal. Nickel is 5%-62% of the metal; the average is 10%. Average cobalt content is 0.5%. We know this from iron meteorites. I
treat meteorites as a good sample of near Earth asteroids. Precious metals will also be present. Gold tends to bind to iron, so any iron deposit will
have gold mixed with it. Platinum follows nickel. All iron meteorites have measurable quantities of gold, silver, platinum, and all of the other
platinum group metals: ruthenium, rhodium, palladium, osmium, and iridium. These 8 precious metals appear to be present in relatively low amounts, but
can be easily concentrated to commercially mineable quantities.
Meteorites have a lot of published data, but it's hard to get complete data. One iron meteorite, Allan Hills 84233, has 1070 parts per billion gold;
iron and other precious metals are not reported. The bulk average for CI meteorites is 145ppb gold, but much more platinum. If the ratio of
gold:platinum holds the same this would provide a great deal of platinum in an iron asteroid. This can be concentrated by simple means: grind the
asteroid into iron filings, centrifuge it and use a magnet to collect magnetic particles. This would collect metal and discard the mineral inclusions.
Then use the Mond process to extract ferrous metals. This works by pressurizing the ore in pure carbon monoxide and heating to 50°C, nickel with
combine to form nickel-carbonyl gas. That gas is drawn off and heating in a second chamber to 230°C which breaks it down, precipitating nickel leaving
carbon monoxide. This cycle is used commercially to produce 100% pure nickel. It also works with iron and cobalt, although they have slightly
different pressures and temperatures. This produces iron, nickel, cobalt, or iron/nickel alloy with highly controlled proportion. It also leaves
behind everything else from the metal. The left-overs will have highly concentrated precious metal.
Typical M-type asteroid, metal portion:
88% iron, 10% nickel, 0.5% cobalt, 1.5% everything else.
Precious metal - ppb - troy ounces per short ton of ore - concentrated ounces/ton
Gold - 1070 - 0.0312 - 2.08
Silver - 1476 - 0.0430 - 2.86
Platinum - 7379 - 0.215 - 14.3
Ruthenium - 5239 - 0.15 - 10
Rhodium - 1033 - 0.0301 - 2.0
Palladium - 4132 - 0.12 - 8.0
Osmium - 3616 - 0.105 - 7.0
Iridium - 3431 - 0.100 - 6.67
Resoures will not be a problem if we can get into space easy and for cheap