Reverse circulation (RC) drilling utilizes a solid bit (usually tri-cone) to produce a hole and delivers rock chips to the surface for subsequent analysis. This type of drilling uses a large, rotary drill and a compressor to blow the rock chips produced by the bit to the surface. The air is blown down the annulus between the rock wall and the drill pipe or, more commonly, down a special annulus in the drill pipe. The air and rock chips are then blown past the bit and up inside the drill pipe to the surface. Normally the air exhausts through a centrifugal classifier so that the rock chips and dust will be captured in a sampler.

The reverse circulation drills are all truck mounted and so must have good road access to the drill site therefore are no good for remote drill camps. However, the cost of drilling is much less than diamond drilling and the penetration rates are an order of magnitude greater than diamond drills. For this reason, may drill campaigns start with reverse circulation drills and move to diamond rigs if the mineralization warrants it.

Unlike diamond drills, RC drills do not produce a core which comes sequentially from the hole. The rock chips created by the drill bit are delivered to the surface generally in the order in which they are produced but not always. Therefore, RC drilling is not as accurate as diamond drilling. There is no way of knowing with certainty where the chips are from. Also there is a tendency for heavier minerals (eg gold) to fall to the bottom of the hole or be caught in elbows and curves in the drill pipe. As a result, assays from RC drill samples may understate the amount of mineralization present in the rock.

Nevertheless the relatively higher speed and low cost of RC drilling makes it a popular method for obtaining mineral samples for assaying.