Question: In which district of the Badakhshan Province is the settlement located which is famous for its ancient mines, which produce a deep blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color, and are said to produce the world's finest of this stone?
Sentence (from "Blue diamond"): Blue diamonds range in grade from Flawless to Included, just as in the case of white diamonds.
Relevant evidence: No