| Abutment - In
coal mining, (1) the weight of the rocks above a narrow roadway is transferred to the
solid coal along the sides, which act as abutments of the arch of strata spanning the
roadway; and (2) the weight of the rocks over a longwall face is transferred to the front
abutment, that is, the solid coal ahead of the face and the back abutment, that is, the
settled packs behind the face. |
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| Acid deposition or acid rain
– Refers loosely to a mixture of wet and dry "deposition"
(deposited material) from the atmosphere containing higher than "normal" amount
of nitric and sulfuric acids. The precursors or chemical forerunners of acid rain
formation result from both natural sources, such as volcanoes and decaying vegetation, and
man-made sources, primarily emissions of sulfur and nitrogen oxides resulting from fossil
fuel combustion. |
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| Acid mine water - Mine
water that contains free sulfuric acid, mainly due to the weathering of iron pyrites. |
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| Active workings - Any
place in a mine where miners are normally required to work or travel and which are
ventilated and inspected regularly. |
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| Adit - A
nearly horizontal passage from the surface by which a mine is entered and dewatered. A
blind horizontal opening into a mountain, with only one entrance. |
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| Advance - Mining
in the same direction, or order of sequence; first mining as distinguished from retreat. |
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| Aerial Survey - A survey made from a flying aircraft, such as photograohic,
magnetometer, radioactivity, etc. |
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| Air Blast - The sudden failure of walls or pillars in a mine causing a rush of air
throughout the mine. |
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| Air split - The
division of a current of air into two or more parts. |
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| Airway - Any
passage through which air is carried. Also known as an air course. |
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| Alteration - Any
physical or chemical change in a rock or mineral susequent to its formation. |
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| Alluvial - A sediment or gravel deposited by the
action of a stream or river in a river bed, flood plain, lake, fan at the foot of mountain
slopes, or in estuaries that may or may not contain diamonds or precious minerals or both; |
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| Amalgam - An alloy
of mercury with another metal. |
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| Amalgamation - A
process by which gold and silver are extracted from an ore by dissolving them in mercury. |
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| Amex - Consists of
free-flowing, carefully blended, plant mix of ammonium nitrate prills and oil to which
special ingredients have been added for reducing the generation of static electricity
during pneumatic loading operations and preventing caking of the blasting agent when in
storage. |
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| Anemometer -
Instrument for measuring air velocity. |
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| Anfo - Ammonium
nitrate - fuel oil blasting agent. |
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| Anodet Delay - A
non-electric, millisecond delay unit which is initiated with B-line detonating fuse. |
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| Angle of dip -
The angle at which strata or mineral deposits are inclined to the horizontal plane |
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| Angle of draw - In
coal mine subsidence, this angle is assumed to bisect the angle between the vertical and
the angle of repose of the material and is 20° for flat seams. For dipping seams, the
angle of break increases, being 35.8° from the vertical for a 40° dip. The main break
occurs over the seam at an angle from the vertical equal to half the dip. |
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| Angle of repose - The
maximum angle from horizontal at which a given material will rest on a given surface
without sliding or rolling. |
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| Anomaly - A term
applied to a departure from the normal or field characteristic, commonly used in
geophysical prospecting. |
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| Anticline - An
upward fold or arch of rock strata.
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| Aquifer - A
water-bearing bed of porous rock, often sandstone.
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| Arching - Fracture
processes around a mine opening, leading to stabilization by an arching effect. |
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| Area (of an airway)
- Average width multiplied by average height of airway, expressed in square feet. |
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| Assay laboratory - A
laboratory in which the proportions of metal in ores or concentrates are determined using
analytical techniques |
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| Assessment work -
The amount of work specified by law, which must be done each year to retain legal control
of mining lands. |
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| Auger - A
rotary drill that uses a screw device to penetrate, break, and then transport the drilled
material (coal). |
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| Autoclave system:
an oxidation treatment in which high temperatures and pressures are applied to convert
refractory gold-bearing sulfide materials into amenable oxide ore. |
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| Autogenous grinding
- The process of grinding in a rotating mill which uses a grinding medium of large ore
pieces , instead of conventional steel balls or rods. |
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| Auxiliary operations -
All activities supportive of but not contributing directly to mining. |
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| Auxiliary ventilation -
Portion of main ventilating current directed to face of dead end entry by means of
an auxiliary fan and tubing. |
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| Azimuth - A
surveying term that references the angle measured clockwise from any meridian (the
established line of reference). The bearing is used to designate direction. The bearing of
a line is the acute horizontal angle between the meridian and the line. |
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