Scary Kerry.

It's a well-known fact... I recently took an advanced astronomy class as an elective to my executive-MBA studies. Things have changed since science class 30 years ago...

What we see at the earth's crust and availability for mining is a tiny fraction of what was formed as the earth accreted pieces & parts during the solar system formation. The heavy / molten iron core strongly attracted heavy metals into the inner-earth. What is here now is what was pelted by asteroids after the planet's initial formation and is generally trapped from sinking lower at the bedrock layer. The rocky nature of earth is just the light stuff that didn't fall into the core.

Asteroids don't have any gravitation to speak of, so the same building blocks of the solar system (and earth) are present on them as well, albeit consistent throughout them in percentages and just requiring extraction & separation through typical lode-mining processes. you are not going to be panning for gold on the surface of one, as the ores will be mixed thoroughly. But its not a problem for separation techniques already in use.

Asteroids come in several types, mainly 2, light rocky stuff like you spoke of and is probably "most" of them, these are the ones that burn-up readily when skipping across our atmosphere, and others are heavy metals that leave impact craters as they usually have something left that hits with some force. The meteor crater in Arizona is a good example, but was only about the size of a VW beetle. The ones we are talking about would have the same heavy composition and are miles across. There's not a mine anywhere on earth that has a vein of miles wide & long of heavy & useful metals. Of course, we're also talking billions or trillions of asteroids.

"In fact, all the gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium, ruthenium, and tungsten mined from Earth's crust, and that are essential for economic and technological progress, came originally from the rain of asteroids that hit Earth after the crust cooled.[8][9][10] This is because although asteroids and Earth accreted from the same starting materials, Earth's relatively stronger gravity pulled all heavy siderophilic (iron-loving) elements into its core during its molten youth more than four billion years ago.[10] This left the crust depleted of such valuable elements[10] until asteroid impacts re-infused the depleted crust with metals (some flow from core to surface does occur, e.g. at the Bushveld Igneous Complex, a famously rich source of platinum-group metals)."

Economics[edit]
Currently, the quality of the ore and the consequent cost and mass of equipment required to extract it are unknown and can only be speculated. Some economic analyses indicate that the cost of returning asteroidal materials to Earth far outweighs their market value, and that asteroid mining will not attract private investment at current commodity prices and space transportation costs.[32][33] Other studies suggest large profit by using solar power.[34][35] Potential markets for materials can be identified and profit generated if extraction cost is brought down. For example, the delivery of multiple tonnes of water to low Earth orbit for rocket fuel preparation for space tourism could generate a significant profit.[36]

In 1997 it was speculated that a relatively small metallic asteroid with a diameter of 1.6 km (0.99 mi) contains more than $20 trillion USD worth of industrial and precious metals.[6][37] A comparatively small M-type asteroid with a mean diameter of 1 kilometer (0.62 mi) could contain more than two billion metric tons of iron–nickel ore,[38] or two to three times the annual production of 2004.[39] The asteroid 16 Psyche is believed to contain 1.7×1019 kg of nickel–iron, which could supply the world production requirement for several million years. A small portion of the extracted material would also be precious metals.

Although Planetary Resources says that platinum from a 30-meter long asteroid is worth 25–50 billion USD,[40] an economist remarked that any outside source of precious metals could lower prices sufficiently to possibly doom the venture by rapidly increasing the available supply of such metals.[41]

Development of an asteroid-orbit manipulation infrastructure could offer an irresistible return on investment.[42] However, astrophysicists Carl Sagan and Steven J. Ostro raised the concern that altering the trajectories of asteroids in nearby interplanetary space could cause a catastrophic collision with Earth. These scientists conclude that stringent controls on the misuse of orbit-engineering technology be instituted.[42][43][44]

Exactly. You must be referring to the Santa Susanna Mountains over looking the San Fernando Valley. We used to laugh when we tested the bigger ones late at night. The biggest we ran up there was the J-2 (110,000 #s thrust). The F-1's (1,522,000 #s of thrust) were only tested at Edwards AFB up in the Antelope Valley. I sure miss that job, it was the greatest. My dad worked at Lockheed Skunk Works. We almost weren't allow to talk to each other.