Core drilling is a system that drills and collects a core (cylindrical) sample in the state it is found, i.e. in-situ. The system used is known as ‘wireline coring’ where a diamond impregnated (hollow) core bit is used. The core bit cuts until the core barrel is full while the drilling mud/cutting oil both cools/lubricates the bit and acts as a medium for lifting the cuttings to the surface.