I had a slightly diferent take on the situation, intrepreting it as, there were some metals to be found, but they were as scarce on that planet as say, diamonds or gold is here on earth - relatively rare but still available.
Interesting how different readers intrepret a situation - but that's what makes the books so special - we all create a slightly different world in our minds that we feel comfortable living in while we're reading.
And if they were made of bifg diamonds, I'd love to be a blacksmuith on Midkemia. I'd trade metal swords, shovels, hoes, etc, all day long for their equivalent weight in diamonds...
