fed the European market.

In the 1970s, outside of the oil and gas industry, roller bits using mud circulation were replaced by the first pneumatic reciprocating piston Reverse Circulation (RC) drills. The former became essentially obsolete for most shallow drilling, now only used in certain situations where rocks preclude other methods. RC drilling proved much faster and more efficient. It continues to improve with better metallurgy, deriving harder, more durable bits and new compressors capable of delivering higher air pressures at higher