I was assuming you'd have parachutes to avoid vaporizing the rocks when they hit the ground.

And if we have parachutes then we can wrap an ablative capsule around the rocks.

Add a guidance system to make the lawyers and citizens happy.

I think parachutes would be a waste, but a cheap, spray-on ablative layer could make sense.

Think of it this way - with parachutes and a guidance system you can land the stuff wherever you want.

This might not be so important for tons of raw metal. Could be a good tech to have around when you want your orbital factories to compete with terrestrial concerns.

And where would you get the parachutes, ablative capsule and guidance system?

Make them in orbit.

or

Send them up as freight.

Gold is rare everywhere; is there any evidence that there's a large amount of it floating around the asteroid belt?

Yes, because Gold is not rare everywhere, just in the Earth's crust because of gravity differentiation (Gold sinks--there's probably quite a bit of it in the mantle/core).

There are individual asteroids out there with more platinum-group elements than has been extracted from the Earth in all of human history.

Yes. 433 Eros is estimated to contain something on the order of $100 trillion worth, with similar amounts of other valuable elements.

There is some evidence that most of the precious metal deposits on earth came from collisions with such asteroids.

I've done quite a bit of looking around re: 433 Eros's composition. I have found very little to suggest to me that there's large amounts of valuable minerals there. Can you cite someone that's done a composition extimate? This: http://www.psrd.hawaii.edu/Feb02/eros.html suggests such estimates are spotty at best, since the formation of the object hasn't even fully been agreed upon.

I'd welcome the evidence about precious metals coming from collisions, that meshes with some of my understanding of the early solar system, but would be glad to know more.

Does that estimate take into account the way such vast amounts affect the price curve? I would think that the gold price will fall if it is available in abundance.