A means by which hollow steel rods with a diamond bit attached are driven into solid rock by a high speed rotary motion. A cylindrical core of rock is recovered for the purpose of obtaining geological, metallurgical or analytical information.

Just as one should not judge a book by its cover, surface sampling gives no definitive indication of how tremendous, or how mediocre, a deposit lies underfoot. Thus, after surface sampling indicates a possible concentration of valuable mineral, diamond drilling is undertaken. The only way to ascertain the quantity (tonnage) and quality (grade) of a deposit to make a circular cut in the rock and extract the continuous cylindrical core sample from the center of the cut. To do this, a special type of drill has been developed, with a rotating core barrel that grinds down through the bedrock. At the end of the core barrel is a cylindrical bit studded with the hardest of natural substances - diamonds. The size of the diamond drill core varies with the size of the machine used which generally depends on hole depths and material being drilled. However, the common sizes of core are; A - core diameter of 27.0 mm, hole diameter 48.0 mm; B - core diameter of 36.5 mm, hole diameter 60.0 mm; N - core diameter of 47.6 mm, hold diameter 75.5 mm; H - core diameter of 63.5 mm, hole diameter 96.0 mm.

A cylindrical tool impregnated with diamonds is used to dig a hole several centimetres wide and extract a core sample. It reveals the composition of a deep-seated mineral deposit.