a. Method of differential disintegration of closely sized mineral, part of
which explodes and is separable by finer screening. Pryor, 3
b. The breaking up with a crackling noise of mineral substances upon
exposure to heat, as when rock salt is thrown into fire.
c. An obsolete method of tunneling, called fire setting.
A microtexture in metamorphosed rocks, in which axes of contiguous
crystals lie in diverse, crisscross directions that are not random but
rather are part of a definite mechanical expedient for minimizing internal
stress. It is most noticeable in rocks composed largely of minerals with a
flaky or columnar habit. AGI
a. A process resulting from metamorphism, wherein part or all of the
magnesium in a dolomite or dolomitic limestone is used for the formation
of magnesium oxides, hydroxides, and silicates (e.g., brucite, forsterite)
and resulting in an enrichment in calcite. AGI
b. Diagenetic or weathering processes wherein dolomite is replaced by
calcite.
A cleaning process in which dust and other fine impurities are removed.
Dedusting is accomplished both by pneumatic means and by dry screening.
Syn:aspirating
To disconnect any circuit or device from the source of power. NCB
a. Workings below the level of the pit bottom or main levels extending
therefrom.
b. Forest of Dean; Lanc. A vein, seam, mine, or bed of coal or ironstone.
c. Term used to designate ocean bottom depressions of great depth, usually
deeper than 6,000 m. Hy
A method for examining the mineral particle content of drilling water. In
this method, a glass cell is filled with the water, a little acid is
added, and the sample is placed under a microscope. Dark ground
illumination is used, which shows up the suspended particles. The number
of these is counted, and this number, multiplied by a factor, gives the
number of particles per cubic centimeter. Higham
Eng. Coal seams lying at a depth of 1,800 ft (549 m) or more below the
surface. Fay
The process of cold working or drawing a sheet of strip metal, by means of
dies, into shapes involving considerable plastic distortion of the metal;
e.g., automobile mudguards, electrical fittings, etc. CTD
In continuous wire-line core drilling, a term applied to boreholes 3,000
ft (915 m) or more in depth.
Blasting a quarry or opencast face by using small- or medium-diameter
holes drilled from top to bottom of the face. Nelson
Alluvial deposit of gold or tin stone buried below a considerable
thickness of soil or rock. CF:lead
a. Trans. The first mining properties developed from the surface were
stopped from trespassing beyond their side lines projected downward. The
next mine on the dip of the lode became known as the "deep-level" mine or
"deep."
b. S. Afr. The distinction of deep level and ultradeep level is a vague
one, and has changed with the times. Ultradeep is now a mining level at a
vertical depth of 9,000 ft ( 2.7 km) and over. Beerman
The exploitation of coal or mineral deposits by underground mining
methods. "Deep" is often interpreted as meaning 5,000 ft (1.5 km) or more,
where stresses are high enough to cause sloughing of development openings,
not to mention walls and faces in stopes. However, tectonic horizontal
stresses are greater than gravitational force in many areas. Hence deep
conditions can exist at lesser depths. Indeed, severe rock bursting caused
the closure of a Canadian mine operating at depths of 500 to 700 ft (152
to 213 m). Also, rocks with low strength will produce deep failure
patterns at modest depths, e.g., in Saskatchewan potash mines.
Nelson
A sandy or gravelly bed or bottom of an ancient stream covered by lava.
Applied to widespread strata in the ocean that scatter or return
vertically directed sound as in echo depth sounding. These layers, which
are evidently of biological origin, are located at depths ranging from 150
to 200 fathoms (274 to 366 m) during the day, with most of them migrating
to or near the surface during the night. Abbrev: dsl. Hy
See:plutonic
An ore deposit formed at an estimated depth of 12,000 ft (3.66 km) or
more, at temperatures ranging from 300 to 575 degrees C; e.g., the tin
deposits of Cornwall, England. The deposits are commonly tubular or
veinlike in form, though some are irregular in shape. Lewis
The benchlike feature bordering an elevation of the deep-sea floor at
depths greater than 300 fathoms (1,800 ft or 549 m).
Schieferdecker
The working of 5 to 10 yd (4.6 to 9.1 m) of the coal seam on the dip side
of an advance gate. It gives some protection from crush along the rib side
and also accommodates dirt from the gate instead of conveying it to the
surface. See also:self-stowing gate
Aust. A tall drinking glass; also the drink it contains, so called in
fanciful allusion to the shaft of a mine.