There are two main methods of exploration drilling - core drilling and reverse circulation drilling (usually referred to as RC). Core drilling, yields a solid, cylinder shaped sample of the ground at an exact depth. Reverse circulation (RC) drilling, yields a crushed sample, comprising cuttings from a fairly well determined depth in the hole. Beyond that, the drill hole itself can provide a complementary amount of information, particularly by logging using devices to detect physical anomalies, similar to the geophysical surveys mentioned above.