Mineral exploration drill sampling
Drilling is also an important tool to explore for mineral deposits, including coal. The solid rock core or rock chips (cuttings) that are brought to the surface by drilling are examined and information about any minerals is recorded. As drilling can be very expensive it is generally only used where other exploration methods have shown positive signs of minerals in the earth.
On land, minimum impact drill sampling may include the use of small non-motorised auger-drills that can be carried in an explorer’s backpack. As it is not possible to hand-sample offshore, ship-borne vibration and reverse circulation sampling – both types of drilling - or grab sampling are used to get samples from the seafloor sediments. No equipment is permanently left on the seafloor. Seabed sampling is considered minimum impact when the sampling has a small diameter, is shallow (less than 10 metres below the seafloor) and is widely-spaced across the permit area.
Motorised drilling rigs can range from small ute-mounted drills through to large truck-mounted or platform-mounted rigs (onshore or offshore), which can reach depths of several hundred metres. If need be, where there are no existing roads or tracks, drilling rigs can be flown in using helicopters to minimise environmental effects.