RE: percussion drilling?Current reverse circulation drilling returns the drill cutting up the inside of the dual walled drill pipe. It is a highly accurate sampling system and under most circumstances provides the most accurate sampling of the ore body.
It is true that some structural geologic information is lost but the greatly increased sample provides a much more accurate sample of the ore body.
Increased penetration rate and lower cost of RC drilling contribute to RC use.
Look at it from a practical viewpoint. Is a 1" core a more representitive sample then a 5" round cutting?
(AQ 27mm (1.06 inches) is about 1.5 kg per linear meter vs the about 17 kg for a 5" hole)