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 "Caymanite"): They are mostly small pockets but occasionally reach up to several metres wide.
Relevant evidence: No