In quarrying, the reduction in size or dimension of blasted rock by
additional or secondary blasting. Streefkerk
The main air splits occur at the shaft bottom. In most cases, these splits
are again separated at some point inby and these are called secondary
splits. See also:ventilation; splitting. Nelson
A structure that originated after the deposition or emplacement of the
rock in which it is found, such as a fault, fold, or joint produced by
tectonic movement; esp. an epigenetic sedimentary structure, such as a
concretion or nodule produced by chemical action, or a sedimentary dike
formed by infilling. CF:primary structure
See:sulfide zone
Twinning produced subsequent to the original formation of a crystal.
A vein discovered subsequent to the one on which a mining claim was based;
an incidental vein. CF:discovery vein
Water entering the mine from other workings, as opposed to water inherent
in the area worked by the mine. BS, 10
See:S wave; transverse wave; distortional wave.
A lever whose force is exerted between the fulcrum and the point where it
is applied. Nichols, 1
An ore that needs preliminary treatment before it is of a sufficiently
high grade to be acceptable for shipment or market. CF:first-class ore
Syn:milling ore
A unit of 1 ft3 /s (0.0283 m3 /s). Usually abbreviated
to cusec. Seelye, 1; Hammond
The volume of water represented by a flow of 1 ft3 /s (0.0283 m
3 /s) for 24 hours. It is 86,400 ft3 (2,445 m3
), or nearly 2 acre-feet (actually 1.9835); a convenient unit in storage
computations. Seelye, 1
a. The recovery of pillar coal after first-mining in chambers has been
completed. Hudson
b. The recovery of pillars after development of block pillars by the
multiple entry system has completed a panel.
The correct term for the moment of inertia (I) of the plane area of a
section. Hammond
Aust. Supposed to be due to the ignition of gases developed from highly
heated coal dust, and gases sucked out of the faces of coal by the partial
vacuum resulting from the primary explosion, or liberated by the fall of
roof. CF:retonation wave
An emergency exit from a mine to the surface. Also called second opening;
escapeway. Hudson
The first back ripping on a roadway. See also:back brusher
Nelson
N.S.W. The second-class ore that requires dressing.
A unit of viscosity in drilling mud as measured with a Marsh funnel
according to American Petroleum Institute procedure. Brantly, 1
In mine subsidence, the powerful thrust or pressure, generally 20 to 40 ft
(6 to 12 m) from the face, that causes distance from the roof to the floor
to diminish rapidly and for packwalls to become compressed or pushed down
into a soft bottom. Timber legs or metal supports (if any) in the gates
are generally broken or twisted. Briggs
In anthracite coal mining, one who is required to serve a specified number
of years before being termed a first-class miner. DOT