Mining Terminology - D

Demonstrated reserves – A collective term for the sum of coal in both measured and indicated resources and reserves.

Detectors - Specialized chemical or electronic instruments used to detect mine gases.


Detonator - A device containing a small detonating charge that is used for detonating an explosive, including, but not limited to, blasting caps, exploders, electric detonators, and delay electric blasting caps.

Development - Underground work carried out for the purpose of opening up a mineral deposit. Includes shaft sinking, crosscutting, drifting and raising.

Development drilling - drilling to establish accurate estimates of mineral reserves.


Development mining - Work undertaken to open up coal reserves as distinguished from the work of actual coal extraction.

Diffuser fan - A fan mounted on a continuous miner to assist and direct air delivery from the machine to the face.

Dilution - The contamination of ore with barren wall rock in stoping. Rock that is, by necessity, removed along with the ore in the mining process, subsequently lowering the grade of the ore.

Dip - The inclination of a geologic structure (bed, vein, fault, etc.) from the horizontal; dip is always measured downwards at right angles to the strike.

Directional drilling - A method of drilling involving the use of stabilizers and wedges to direct the orientation of the hole.

Disseminated ore - Ore carrying small particles of valuable minerals spread more or less uniformly through the host rock.


Drift - A horizontal passage underground. A drift follows the vein, as distinguished from a crosscut that intersects it, or a level or gallery, which may do either.

Drift mine – An underground coal mine in which the entry or access is above water level and generally on the slope of a hill, driven horizontally into a coal seam.

Drill - A machine utilizing rotation, percussion (hammering), or a combination of both to make holes. If the hole is much over 0.4m in diameter, the machine is called a borer.


Drilling - The use of such a machine to create holes for exploration or for loading with explosives.

Dump - To unload; specifically, a load of coal or waste; the mechanism for unloading, e.g. a car dump (sometimes called tipple); or, the pile created by such unloading, e.g. a waste dump.