A pivot for a lever. Nichols, 1
A sudden glistening of molten gold or silver at the close of cupellation.
Standard, 2
An irregular, glassy, often tubular or rodlike structure or crust produced
by the fusion of loose sand (or rarely, compact rock) by lightning, and
found esp. on exposed mountain tops or in dune areas of deserts or lake
shores. It may measure 40 cm in length and 5 to 6 cm in diameter. Etymol.
Latin fulgur, lightning. Syn:lightning tube
See:true dip; dip.
A clay or claylike material with a high adsorptive capacity, consisting
largely of the clay minerals montmorillonite and palygorskite. Used
originally in England for whitening, degreasing, or fulling (shrinking and
thickening by application of moisture) woolen fabrics; fuller's earth now
is extensively used as an adsorbent in refining and decolorizing oils and
fats; it is a natural bleaching agent. Its color ranges from light brown
through yellow and white to light and dark green; it differs from ordinary
clay by having a higher percentage of water and little or no plasticity,
tending to break down into a muddy sediment in water. Fuller's earth
probably forms as a residual deposit by decomposition of rock in place, as
by devitrification of volcanic glass. The term is applied without
reference to any particular chemical or mineral composition, texture, or
origin. Syn:walker's earth
The standard type of heading blast consists of a straight in or main
drive, at right angles to the rock face, and a back drive at right angles
to the main drive and parallel to the face. The main drive is normally
driven at quarry floor level to a depth of 0.6 times the height of rock
above the back drive. Apart from exceptional circumstances, the maximum
depth of the main drive should be 50 ft (15 m), so that with faces over 85
ft (26 m) high the 0.6 ratio should not be used, but the main drive
limited to 50 ft. McAdam, 2
With modern drilling equipment, it is now possible, in suitable
conditions, to drill small-diameter holes from top to bottom of the face,
and where this can be done considerable advantages as to cost and
efficiency can be obtained as compared with the bench method. In high
faces of 50 ft (15 m) and upward it is not always easy to drill vertical
holes to give small burdens because of the breakback of the rock at the
crest of the quarry face. It is therefore recommended that larger burdens
be taken and that the vertical holes be supplemented by breast holes at
quarry floor level. These holes are intended to permit concentrated
explosive charges to blow out the toe rock, while the explosive in the
vertical holes brings down the rock from the face. McAdam, 2
a. A cylindrical or tubular object, such as a bit or reaming shell, the
outside and/or inside diameters of which are the size specified. Also
called full size. Long
b. A borehole the inside diameter of which is uniform enough to allow a
new-condition bit to follow portions of the hole drilled by other bits
cutting the same X-borehole size without reaming. Long
c. As applied to deflection drilling, the branch borehole is the same
diameter as the parent hole. Long
A mining system, brought on by the advent of mechanical loading and
mechanical coal cleaning, in which the entire section is dislodged
together and the coal separated from the rock outside of the mine by the
cleaning plant. Kentucky
The greatest amount of subsidence that can occur as a result of mine
workings. See also:percentage subsidence
A condition of teeter in which the maximum degree of fluidization of the
suspension is attained but without disruption of the bed. BS, 5
A rectifier that changes single-phase alternating current into pulsating
unidirectional current, utilizing both halves of each cycle.
Coal Age, 1
In coal mining, a mine in which all development work has reached the
boundaries and further extraction will be done on the retreat.
An explosive compound of mercury, HgC2 N2 O2 , that
is employed for the caps or exploders, by means of which charges of
gunpowder, dynamite, etc., are fired.
A monoclinic mineral, Pb3 Sb8 S15 ; soft metallic
gray; occurs with zinkenite and sphalerite in Romania and Hungary.
An old syn. for brown coal. AGI
a. A hole or a vent from which fumes or vapors issue; a spring or a geyser
that emits steam or gaseous vapor. Usually found in volcanic areas.
AGI
b. The exhalation from a fumarole consists of water vapor, nitrogen,
hydrogen, free hydrochloric acid, hydrofluoric acid, and silicon fluoride.
CF:solfatara; mofette; soffioni. Fay
c. A hole in a volcanic region, from which gases and vapors issue at high
temperature. Webster 3rd
a. The gas and smoke, esp. the noxious or poisonous gases, given off by
the explosion or detonation of blasting powder or dynamite. Fay
b. Consists of very fine particles of metals or metallic compounds that
have been volatilized at the high temperatures of furnaces, condensed at
lower temperatures, and carried by furnace gases into the flues. In
general, all the volatile constituents of the ore charge are represented.
See also:metallurgical fume
A measure of the toxic fumes to be expected when a specific explosive is
properly detonated. Dick, 1
See:basement complex