I recommend Alexi Gilliand's old Rosinante trilogy, which centers on a space based mining operation. Fascinating details well thought out. hey're very old, you would probably need to look for them in a used paperback store.Lack of gravity could be a blessing and a curse in smelting. Likewise the lack of atmosphere.
A large lump of asteroid heated up to the melting point of iron would foam as much of the other stuff turned into gas but can't seperate out because there's not enough gravity. Preasures would build in pockets and suddenly escape in random directions, making quite a mess of your mining operation.
To smelt in space you would want to first break your ore up so that it can't trap the out gasses. You might also want to roast it to make some things gas out first. This is already done with many ores to reduce their weight for shipping.
Next you put your ore in sealed crucible. Use solar mirrors or electric induction to heat the stuff up. You can inject oxygen just like modern terrestial steelmills do to oxidize out the impurities.
Spin your crucible to cause centripital seperation of the liquid metals and tap out the perimeter. The heaviest metals will squirt out like a pinwheel, radiate their heat and cool into pellets that will impact on a belt-like target.
Lots of experimentation is required. But it can be done on a vast scale because your structures won't have to stand up to planetary gravity.
Timing is everything. The first stuff out would probably be a soup of rare and heavy metals that you would send off somewhere for further refining.
Even if it was 90% iron and 10% rare metals, it would be an incredibly profitable commodity to sell and probably pay for the whole operation right there. "Good morning, the price per megaton of 'first tap' on the Ceres market rose seven tenths on announcement of the approval of the..."
Can you picture it?
[This message has been edited by Ted Galacci (edited March 04, 2006).]