There are two principal ways of extracting diamonds, from the volcanic pipes and from alluvial deposits.
1. A diamond pipe or chimney is worked first in open cast mining. As the mine gets deeper, shafts are sunk parallel to the pipe, from which horizontal tunnels are cut to extract the "blue ground" or "Kimberlite" rock where the diamonds have been formed.
2. In alluvial mining, diamonds are extracted from the beds of ancient rivers or from beaches by the sea, where they have been washed and carried over time from the volcanic pipes