In which one of the following districts, have large reserves of diamond-bearing kimberlite been discovered in the recent past?

1. In the recent past (relative to 2007), significant reserves of diamond-bearing kimberlite were discovered in the Raipur district of Chhattisgarh. 2. Kimberlites are igneous rocks best known for sometimes containing diamonds. 3. While other districts might have mineral reserves, the large discovery mentioned in the question pertains to Raipur.