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Asteroids contain precious metals like gold, silver, platinum, and the other platinum group metals: palladium, irridium, rhodium, osmium, and ruthenium.
A reasonable sample of Near Earth Objects are meteorites, these are objects that have collided with Earth. Not all asteroids have been assayed for precious metals, but a few have.
M-type (metal) asteroids are also known as iron-nickel because they are composed primarilly of iron/nickel alloy as metal. This is not an oxidized ore, this is pure metal.
The Mond process uses carbon monoxide to extract absolutely pure metal. It's easy, but doesn't work with oxidized minerals. It will work with M-type asteroids, but not others.
After extracting iron and nickel, everything else is concentrated. The important statistic is the concentration of gold after removing iron and nickel.
Unfortunately, published assays for gold include very few M-type meteorites. We need to assay M-type meteorites for all precious metals to obtain a reasonable sample.
M-type asteroids are 5%-62% nickel and often more than 90% iron, but on average and are 88% iron, 10% nickel, 0.5% cobalt.
Although they're almost pure metal, they often have inclusions of rocky minerals; up to 30%.
The M-type meteorites listed below do not have published iron concentration or inclusions, so for the sake of estimation it is assumed that the ore is crushed and magnetically separated, leaving 98.5% ferrous metal.
|Meteorite||Type||Gold (ppb)||Gold (troy ounces/ton)||Gold after concentration (troy ounces/ton)|
|Allan Hills 84233||iron||1070||0.0312||2.08|
|Hvittis (magnetic portion)||H 6|| 690||0.0201|
|Hvittis (non-magnetic)|| 15||0.00044|
|Fayetteville (light portion)||H|| 210||0.00612|
|Fayetteville (dark)|| 200||0.0058|
|Leighton (light portion)||H 5|| 192||0.0056|
|Leighton (dark)|| 251||0.00732|
|Leighton (dark)|| 370||0.0108|
|Leighton (dark, crushed after irradiation)|| 115||0.00335|
|Pantar(light portion)||H 5|| 198||0.00578|
|Pantar (dark)|| 180||0.00525|
|Pantar (dark)|| 202||0.00589|
|Tysnes Island (light portion)||H 4|| 254||0.00741|
|Tysnes Island (dark)|| 211||0.00615|
|Weston (light portion)||H 4|| 240||0.0070|
|Weston (dark)|| 218||0.00636|
|Beaver Creek||H|| 200||0.0058|
|Beaver Creek|| 280||0.00817|
|Tagish Lake||C|| 190||0.00554|
M-type (metal) asteroids are mostly iron and nickel, with a little precious metal, but also has some magnesium.
C-type (carbonaceous) asteroids are hydrated minerals (epsomite, gypsum, clay), tar, carbonates (calcite, siderite, magnesite), and condrules (pebbles).
The hydrated material is an excellent source of water from which you can make rocket fuel.
The tar might have tiny ice crystals, but only deep in the interior where sunlight couldn't boil it off.
Tar and carbonates are a source of carbon which can be combined with iron to make steel. The condrules have other metals that can be added to steel.
They also have some iron, but it's oxide minerals which must be smelted.
Industrial metals can be made from elements found in asteroids. Iron and carbon combine to make steel, however other elements are added to make various alloys.
Manganese (Mn) is normally present in all steel and functions as a deoxidizer. It also imparts strength and responsiveness to heat treatment. It is usually present in quantities of 0.5-2.0%.
Nickel (Ni) increases strength and toughness but is rather ineffective in increasing hardness. It is generally added in amounts ranging from 1-4%. In some stainless steels it is sometimes as high as 36%.
Chromium (Cr) increases the depth penetration of hardening processes and also the responsiveness to heat-treatment. It is usually added with nickel for use in stainless steels. Most of the chromium-bearing alloys contain 0.5-1.5% chromium; some stainless steels contain as much as 20%. It can affect forging, causing a tendency in the steel to crack.
Vanadium (V) retards the grain growth of steel, even after long exposures at high temperatures, and helps to control grain structures while heat-treating. It is usually present in small quantities of 0.15-0.20%. Most tool steels which contain this element seem to absorb shock better than those that do not.
Molybdenum (Mo) adds greatly to the penetration of hardness and increases toughness of an alloy. It also causes the steel to resist softening at high temperatures, which defeats the purpose of forging.
Silicon (Si) has a beneficial effect upon tensile strength and improves hardenability of an alloy. It has a toughening effect when used in combination with certain other elements. Silicon is often added to improve electrical conductivity of an alloy, and its average concentration is 1.5-2.5%.
Tungsten (W), also known as wolfram, is often used as an alloying element in tool steels as it tends to impart a tight, small, and dense grain structure and keen cutting edge when used in relatively small quantities. It will also cause a steel to retain its hardness at higher temperatures and hence will have a detrimental effect upon the steel's forgeability (red hard).
Sulphur (S) is usually regarded as an impurity in most alloys and its addition to steel is held to a minimum as it is damaging to the hot-forming properties of a steel. It is, however, added to screw stock as it does increase machinability.
Lead (Pb) increases the machinability of steel and has no effect upon the other properties of the metal. It is usually added to an alloy only upon request and then in quantities of 0.15-0.30%.
Phosphorus (P) is present in all steel. It increases yield strength and reduces ductility at low temperatures. It is also believed to increase resistance to atmospheric corrosion. Phosphorus is, however, treated as an impurity in most alloys.
Some forms of steel are:
O-1: coldwork die steel, C 0.9%, Cr 0.5%, Mn 0.5%, W 0.5%
W-1: tool steel, C 0.6-1.4%
W-2: tool steel (files), C 0.6-1.4%, V 0.25%
1095: clock springs, C 0.90-1.03%, Mn 0.3-0.5%
5160: leaf springs, C 0.56-0.64%, Cr 0.7-0.9%, Mn 0.75-1.00%, P 0.035% max, Si 0.15-0.35%, S 0.04% max
L6: saw blades, C 0.7-0.9%, Cr 0.03%, Mn 0.35-0.55%, Ni 1.4-2.6%, V 0.15%, P 0.025%, Si 0.25%, S 0.01% max
S-1: designed to absorb shock rather than resist abrasion or wear, C 0.5%, Cr 1.5%, W 2.5%
S-5: like S-1 but tougher & harder (jackhammer bits), C 0.55%, Mn 0.8%, Mo 0.4%, Si 2.0%
440-C: stainless steel (knives), C 0.95%-1.2%, Cu 0.5% max, Cr 16-18%, Mn 1% max, Mo 0.65%, Ni 0.75% max, P 0.04% max, Si 1% max, S 0.03% max
M-2: high-speed tool steel, C 0.85%, Cr 4.15%, Mn 0.35%, Mo 5%, Si 0.3%, W 6.4%, V 1.95%
Vasco Wear: very tough and wear resistant, abrasives barely cut it, blade simply doesn't get dull (edge must be forged), C 1.12%, Cr 7.75%, Mn 0.3%, Mo 1.6%, Si 1.2%, W 1.1%, V 2.4%
Other industrial metal alloy:
Inconel 617: super-high temperature alloy (metalic Thermal Protection System), Ni 44.5%, Cr 20-24%, Co 10-15%, Mo 8-10%, Fe 3% max, Al 0.8-1.5%, Mn 1% max, Si 1% max, Ti 0.6% max, Cu 0.5% max, C 0.05-0.15%, S 0.015% max, B 0.006% max
Meteorite Research, Edited by Peter M. Millman
The Fall, Recovery, Orbit, and Composition of the Tagish Lake Meteorite: A New Type of Carbonaceous Chondrite, Science, Vol 290, 13 October 2000
Catalogue of Meteorites, Edited by Monica M. Grady, The Natural History Museum 2000
The Complete Bladesmith, Jim Hrisoulas, ISBN 0-87364-430-1