a. In bituminous coal mining, one who works in rock or slate as
distinguished from coal. Also called rock shooter; slate driller.
DOT
b. See:rock splitter
A hard heading or stone drift. Nelson
a. The general name for any kind of inert dust used in rendering coal dust
inert or in filling rock-dust barriers. Equivalent to the British stone
dust. Rice, 2
b. The dust produced in mines by blasting, drilling, shoveling, and
handling rock. Rock dust in suspension varies in particle size and
composition. The most dangerous dusts are silica, sericite, and asbestos;
but all fine dusts are health hazards when inhaled. The smaller sizes, 10
microns and less, are more dangerous than the larger sizes. Wet drills,
sprays, water infusion, and ample ventilation are employed to reduce the
dust menace. See also:dust consolidation; dust-free conditions;
stone dust; stone-dust barrier. Nelson
a. A device that releases a large quantity of inert dust in the air in the
path of an explosion, extinguishing the flame. Rice, 2
b. A series of troughs or shelves laden with rock dust and so arranged
that the air waves from an explosion will trip them and fill the air with
rock dust and thus quench the flame of exploding coal dust.
a. A machine that distributes rock dust over the interior surfaces of a
coal mine by means of air from a blower or pipeline or by means of a
mechanical contrivance, to prevent coal dust explosions. Also called
rock-dust machine.
b. See:rock-dust man
a. The dusting of underground areas with powdered limestone to dilute the
coal dust in the mine atmosphere and on the mine surfaces, thereby
reducing explosion hazards.
b. A very widespread control measure used in coal mines to combat
explosive dusts. By machine, inert (combustible) dust is sprayed, dry or
wet, on the roof, floor, and ribs in all working places and haulageways,
to reduce the explosibility of settled coal dust. The Mine Safety and
Health Administration requires rock dusting to within 40 ft (12 m) of the
face. The incombustible content of settled dust samples after rock dusting
must constitute 65% or more by weight, with an increase of 1% for each
0.1% methane present. A dust as nearly inert, physiologically, as
possible, should be employed in rock dusting; limestone (calcium
carbonate) is most widely used. Hartman, 2
A machine consisting essentially of a flexible hose fed by a powerful
blower. It is used in forcing rock dust, usually powdered limestone, onto
the floor, walls or ribs, and rooms and entries of a mine, thereby making
the coal dust nonexplosive.
In bituminous coal mining, a laborer who sprinkles rock dust by hand or
with a machine throughout mine workings as a precaution against
explosions. Syn:rock duster
DOT
This kit is designed to prevent coal-dust explosions. It helps to
determine the explosion hazard prior to rock dusting, the fineness of the
rock dust as it comes from the pulverizer, and the percentage of
combustible matter present in rock and coal dust mixtures after rock
dusting. Best, 1
A section of a mine entry, the ribs, roof, and floor of which have been
coated with rock dust. Rice, 2
a. A small digging bucket mounted on two rocker arms in which auriferous
alluvial sands are agitated by oscillation, in water, to collect gold. A
shortened term for rocker shovel; rocker arm shovel.
b. Used for testing placer deposits and for working pockets and small
placer deposits. The gold-bearing gravel is placed on the screen; gold and
fine sand are washed through the screen, and remaining stones are cleaned
out. A chute directs the material to the upper end of the bottom, which
may be covered with small transverse riffles or canvas. Waste material
passes over a tailpiece at the end of the rocker. Rockers range in length
from 6 to 12 ft (2 to 4 m), and in bottom width from 14 to 20 in (35 to 50
cm), with holes in the screens from 1/4 to 1/2 in (0.6 to 1.2 cm) in
diameter. The slope of the rock should be adjusted to the nature of the
gravel and is commonly 1 in 12, ranging from 1 in 8 to 1 in 20. Two
workers with a rocker can handle from 3 to 5 yd3 (2.3 to 3.8 m
3 ) of gravel in place in 10 h if the ground is easily rocked.
Lewis
c. A portable sluicebox used by prospectors and fossickers in treating
alluvial mineral deposits. Also called rocking cradle. Pryor, 3
a. A lever resting on a curved base so that the position of its fulcrum
moves as its angle changes. Nichols, 1
b. A bell crank with the fulcrum at the bottom. Nichols, 1
See:rocker shovel
See:rocker
Among the smaller capacity cars, the most popular and most widely used are
the gravity dump types, such as rocker dump and scoop cars, designed so
that the weight of the load tips the body when a locking latch is released
by hand. The body of this type is balanced to right itself after the load
is discharged. Rocker dump cars range in capacity from 1 yd3
(0.76 m3 ) handloaded types, to units of 10 yd3 (7.6 m
3 ) for power shovel loading. Pit and Quarry
A digging and loading machine consisting of a bucket attached to a pair of
semicircular runners that when rolled, lifts and dumps the bucket load
into a car or other materials transport unit behind the machine.
A miner's cradle or rocker, a cradlelike device for washing out mud from
the contents of a dredge. Mathews
In situ removal of all firm, unaltered, and unweathered surface geological
materials.
See:fabric
Fracture or failure of a rock that has been stressed beyond its ultimate
strength. AGI