See:straight work
a. A relatively wide launder or sluice set at a slope and covered with a
blanket or corduroy for catching comparatively coarse gold and valuable
mineral. See also:blanket strake
b. A trough in which ore, gravel, etc., are washed; a launder.
Standard, 2
c. The place where ore is assorted on the floor of a mine; a dressing
floor. Standard, 2
Term for wire rope with one or more broken strands. Pryor, 3
See:preformed rope; multistrand rope; flattened strand rope.
A triclinic mineral, (Zn,Cu)3 (AsO4 )2 ; blue; at
Tsumeb, Namibia.
a. A bar; a beam; a coal face bar. Mason
b. A thin bar or metal plate, similar to a fishplate, used to secure
together butt-jointed timber or steel members. Hammond
A brake generally used on small winding engines. Sinclair, 5
Flattened bars of iron with holes punched through them for bolts. The
holes are made somewhat larger than the bolt to permit rail expansion and
contraction. Kiser
A system of haulage (usually endless rope) in which the engine is
installed on the surface, and the power is transmitted to the haulage
drums at the pit bottom by means of a rope, which is known as a strap
rope, or a driving rope. This rope merely transmits power and is distinct
from the haulage rope. Nelson
Thin metal support members from 5 to 20 ft (1.5 to 6 m) long are bolted to
the mine roof to prevent roof deterioration between the bolts. Also known
as roof mats or bacon skins.
Plural of stratum.
A bolt or rod, from 2 to 5 ft (0.6 to 1.5 m) or more in length, set in
drill holes in the strata for the support of curbs, skeleton tubbing,
helical steel supports, etc., in shafts and staple shafts. In general, the
weaker the ground, the longer the bolts. CF:roof bolting
Nelson
Said of a mineral deposit confined to a single stratigraphic unit. The
term can refer to a stratiform deposit, to variously oriented orebodies
contained within the unit, or to a deposit containing veinlets and
alteration zones that may or may not be strictly conformable with bedding.
AGI
See:roof control
These occur in the mineral deposit itself or in adjacent or nearby
formations. Their origin may be in a particular formation in which they
were laid down or formed subsequently by chemical action, or they may
occasionally migrate into other formations, frequently because of release
of pressure with mining. Water flow and rock porosity and fissures also
allow gas migration. The principal strata gases are methane, carbon
dioxide, nitrogen, sulfur dioxide, hydrogen sulfide, and radon.
Hartman, 1
An apparatus inserted in the drill hole that permits engineers to make a
visual inspection of the strata. Coal Age, 3
The strata temperature is determined by the surface temperature, the
diffusivity of the strata, and the emissivity of the surface. With rocks
of high thermal conductivity, and thus, high diffusivity, as in metal
mines, the increase in temperature with depth is small, i.e., the
geothermic gradient is low. Where rocks have low thermal conductivity, as
in coal measure strata, the geothermic gradient is steep.
Syn:geothermic gradient
strategic and critical material
Materials that (a) would be needed to supply the military, industrial, and
essential civilian needs of the United States during a national emergency,
and (b) are not found or produced in the United States in sufficient
quantities to meet such need. Strategic
Ruby and nonruby block mica. Good-stained or better qualities, grade No. 6
or larger; ruby-stained A/B quality, grade No. 6 or larger; ruby and
nonruby film, first and second qualities, grade No. 4 and smaller;
muscovite and phlogopite splittings; and phlogopite block of high heat
quality. Skow
Minerals essential to the national defense, for the supply of which,
during war, we are wholly or in part dependent on foreign sources, and for
which strict measures controlling conservation and distribution are
necessary. For example, chromium- and tin-bearing minerals, quartz
crystal, and sheet mica were some of the "strategic minerals" during World
War II.
Characterized by numerous very thin parallel layers, whether separable or
not, either of sedimentary deposition (as a bed of clay) or of deposition
from solution (as in a stalagmite or banded agate). AGI