Answer:
A certain wizard resided in a city made from this gemstone.
If a man carried my burden, he would break his back. I am not rich, but leave silver in my track.
What has one eye but cannot see?
Stealthy as a shadow in the dead of night, cunning but affectionate if given a bite. Never owned but often loved. At my sport considered cruel, but that's because you never know me at all.
I can be written, I can be spoken, I can be exposed, I can be broken.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.