One who operates conical rolls that separate stone from clay, preventing
machine from jamming by regulating flow of clay into it. DOT
A uranium and/or vanadium orebody in a sandstone lens or layer, which cuts
across bedding in sharply curving forms, commonly C-shaped or S-shaped in
cross section. Two types can be distinguished: the Colorado Plateau type,
named in 1956, and the Wyoming type, named in 1962. Roll orebodies of the
Colorado Plateau type are of highly variable geometry, with their longest
dimension in plan view parallel to the axes of buried sandstone lenses
representing former stream channels, and surrounded by a wide halo of
reduced (altered) rock. Orebodies of the Wyoming type are crescent-shaped
in cross section and typically form in relatively thick, tabular, or
elongate sandstone bodies, with the tips of the crescent thinning and
becoming tangent to mudstone layers above and below.
See also:roll-front orebody
See:mill scale
A screen consisting of a number of horizontal rotating shafts, fitted with
elements arranged to provide screening apertures. BS, 5
a. A commercial name for sulfur that has been purified and cast into rolls
or sticks. Standard, 2
b. See:brimstone
See:pozzolana cement
A monoclinic mineral, (Ba,H2 O)Mn5 O10 ; rare as
single crystals; commonly intergrown with other manganese oxides. Formerly
called psilomelane, a term now reserved for mixtures. CF:hollandite
A yellow, black, or green amber from Romania. Also spelled rumanite.
English
A native ocher of a deep orange-yellow color. Standard, 2
A hollow sphere of opalescent glass with its interior coated with essence
d'orient and then filled with wax.
An isometric mineral, (Ca,Fe,Mn,Na)2 (Sb,Ti)2 O6
(O,OH,F) ; stibiconite group; forms clusters of minute yellow octahedra.
Syn:weslienite
An instrument for measuring changes in vertical height and lateral
movements of the roof relative to the floor at the coal face.
Syn:roof movement meter
Nelson
The crust or scale that forms upon the surface of molten metal in cooling.
Fay
The unit of exposure dose of X-ray or gamma-ray radiation. One roentgen is an exposure dose of X-ray or gamma-ray radiation such that the associated
corpuscular emission per 0.001293 g of air produces, in air, ions carrying
1 electrostatic unit of quantity of electricity of either sign. Designated
by the symbol R. Also spelled roentgen. NCB
Minute wax-yellow to brown, trigonal pyramidal crystals, intergrown with
synchysite, parisite, and bastnasite, from Narsarsuk, Greenland. From
X-ray and optical data, the composition is deduced as Ca2 (Ce,La)
3 (CO3 )5 F3 . Also spelled roentgenite.
Spencer, 5
a. The rock immediately above a coal seam. It is commonly a shale and is
often carbonaceous in character and softer than similar rocks higher up in
the roof strata. The roof shale may contain streaks and wisps of coaly
material, which tends to weaken the deposit. Roof in coal mining
corresponds to hanging wall in metal mining. See also:roof stone
Nelson
b. In mine timbering there are two classifications of roof, the immediate
roof and the main roof. The immediate roof lies directly over the coal and
may be a single layer or several layers of rock material of the same, or
different consistencies, and from a few inches to several feet in
thickness. This roof requires timbering to support it as the coal is
removed. The main roof is the roof above the immediate top, and may vary
from a few feet to several hundred, or even thousands of feet in
thickness. This roof is generally controlled by leaving pillars of solid
coal that will support its weight. Kentucky
c. The country rock bordering the upper surface of an igneous intrusion.
CF:floor
a. A long steel bolt inserted into walls or roof of underground
excavations to strengthen the pinning of rock strata. It is inserted in a
drilled hole and anchored by means of a mechanical expansion shell that
grips the surrounding rock at about 4 ft (1 m) spacing and pins steel
beams to the roof.
b. Syn:rock bolt
c. Current roof bolting consists of steel rods, 5/8 to 1 in (2 to 2.5 cm)
or more in diameter and 3 to 8 ft (1 to 2.5 m) in length, anchored by a
mechanical expansion shell, resin grout, or a combination of both. Grouted
bolts may be fully or partially grouted. A steel plate, sometimes in
combination with wooden headers or steel straps, fits tightly between the
bolthead and mine roof or rib.
In bituminous coal mining, one who reinforces roofs of mine haulageways,
side drifts, and working places with metal or timber to prevent rock and
slate falls. Also called raise driller; stoperman; stoperperson;
timberman. DOT
A system of roof support in mines. Boreholes usually from 3 to 12 ft (1 to
4 m) long are drilled upward in the roof, and bolts of 5/8 to 1 in (2 to
2.5 cm) or more in diameter are inserted into the holes and anchored at
the top by a split cone, mechanical anchor, or resin grout. The bolts are
put up in a definite pattern. The idea is to clamp together the several
roof beds to form a composite beam with a strength considerably greater
than the sum of the individual beds acting separately.
See also:slot-and-wedge bolt; pin timbering; rock bolting.
CF:strata bolt
The scientific study of the behavior of rock undermined by mining
operations and the most effective measures of controlling movements and
failure. The subject is comprehensive, including the systematic
measurement of the movement of strata and the forces and stresses
involved. An attempt is made to correlate data with rock types and the
type of excavation. See also:rock mechanics
A machine cut made in the roof immediately above the seam. A roof cut is
sometimes made in a soft band of dirt over the coal, which gives increased
height in thin seams. The cut is made with a turret coal cutter.
Nelson