Mining Methods (2.05)
Commonly a diamond mine will start off as an open pit dug out in a benched (or staircase) shape that can accommodate a sloping roadway for trucks to drive down to the bottom of the excavation. This design also prevents cave-ins.
Underground mining consists of a large vertical shaft running next to a kimberlite pipe to be used for access to many horizontal tunnels leading into the kimberlite. Diamond-bearing rock is blasted loose at the tunnel faces, hauled to the surface, and processed. Most of the mines vary in types of production. Some produce mostly industrial, others may produce higher qualities. Sometimes tons of rock, gravel or sand have to be processed to retrieve one carat of rough diamond.
The block-cave method is more efficient and more commonly used today. This is simply digging a cave underneath the kimberlite rock until it falls in. The crumbled gravel is more easily processed after it is funneled out into the collection areas.