Sustainable mining is called recycling. I trust that Chris DeWitt (May 24, My Turn) is active in promoting and practicing this activity which reduces impacts on our overflowing landfill, minimizes hazardous wastes, and uses less energy than harvesting raw resources.
Unfortunately, by its very nature, there is no other "sustainable mining." We are unable to assess the practices of mining operations in the future, only their promises; therefore we are left to examine promises and practices in the present and past. The records on those are not what I would call sustainable or environmentally sound.
DeWitt used Websters to define legacy. I turned to the same for sustainable. "Capable of being sustained." Not, capable of being sustained until the ore body runs out (which it will, whether in five years or 50).