a. In this mining method, the ore is excavated in open stopes, retreating
from one end of the stope toward the other. The orebody is developed first
by a series of sublevel drifts above the main haulage level. The sublevels
are connected by a starting raise at one end of the stope and by a
passageway raise for entrance to them and the stope face at the other end.
Chute raises connect the haulage level to the lowest sublevel, at which
the tops of the chute raises are belled out to form mill holes. Beginning
at the starting raise the ore is benched down from the sublevels; the
broken ore falls into the mill holes, where it is drawn off through the
chutes. The stope face is kept nearly vertical as it is benched backward
toward the passageway raise.
b. A mining method involving overhand, underhand, and shrinkage stoping.
Its characteristic feature is the use of sublevels. The sublevels are
worked simultaneously, the lowest on a given block being farthest advanced
and the subs above following one another at short intervals. The uppermost
sublevel underneath the cover is partly caved. The caved cover follows
down upon the caved ore. The broken ore is in part drawn from the level,
and a part remains in the stope to give lateral support to the walls and
to prevent admixture of cover and ore. The breaking faces are developed by
crosscuts, which are extended from wall to wall from the end of the
sublevel. The method can also be looked upon as a retreating method, the
orebody being worked from the top down and the individual blocks upon a
given level being worked from their ends to the center. Modifications of
this method are chamber-and-pillar system; chambers without filling;
combination of subslicing and stoping; drift stoping; filling system;
Mitchell slicing system; pillar robbing; pillar robbing and hand filling;
room-and-pillar system; square work and caving; square work, pillar
robbing, and hand filling; sublevel back stoping; sublevel method;
sublevel slicing system; substoping.
c. A method of mining best adapted to steeply inclined deposits that have
strong ore and strong walls. The ore is usually blocked out by two
horizontal drifts separated vertically by 100 to 200 ft (30 to 61 m) and
raises between the two horizontal drifts, the latter separated by
comparable distances. Vertical pillars may be left between stopes on the
same level, and horizontal ones to support the main haulage. After the
main blocks of ore have been completely mined, it is common practice to
rob the pillars, and the walls of the stope may collapse after the pillars
have been robbed. Lewis
d. Of lodes, open-stope mining in which ore is blasted and drawn through
footwall openings to a gathering level in the country rock below. Used
with strong containing walls and wide lodes. Pryor, 3
e. Of massive deposits, working simultaneously of a series of sublevels
echeloned vertically, the lowest leading and the uppermost being partly
caved as the covered rock descends. Pryor, 3
f. See:sublevel backstoping; substoping.
a. A coating or deposit formed in a glass tube or on charcoal as a result
of heating certain minerals.
b. The product of sublimation. CTD
c. A solid deposit by a gas or vapor; commonly used in reference to
material deposited by volcanic gases. AGI
a. The process by which a solid substance vaporizes without passing
through a liquid stage. CF:evaporation
b. The process of ore deposition, as of sulfur or mercury, by vapors; the
volatilization and transportation of minerals followed by their deposition
at reduced temperatures and pressures. Sublimation deposits are generally
associated with fumarolic activity. AGI
The theory that a vein was filled first with metallic vapors.
To cause to pass from the solid state to the vapor state by the action of
heat and again to condense to solid form.
Generally means land not very good for farming. Tens of millions of tons
of coal are removed each year by stripping the surface of this type land.
Kentucky
A charge of high explosives fired in boreholes drilled in the rock
underwater for dislodging dangerous projections and deepening channels.
Fay
An elongated, steep-walled cleft running across or partially across the
Continental Shelf, the continental borderland and/or slope, the bottom of
which grades continually downwards. AGI
Drilling from the surface of a body of water with a drill mounted on an
anchored tower, platform, or barge. Long
Workings that follow the mineral under the sea. Syn:undersea workings
Zern
Special heavy paper shells in which dynamite is packed in underwater
blasting. Carson, 2
A throat with the fluid level below the bottom of a melter.
See also:throat
The weight of the solids in air minus the weight of water displaced by the
solids per unit of volume of soil mass; the saturated unit weight minus
the unit weight of water. See also:unit weight
a. In an air lift, the distance below the water level, during pumping, at
which the air picks up water. Lewis
b. A term that implies that part of a land area has become inundated by
the sea but does not imply whether the sea rose over the land or the land
sank beneath the sea. AGI
A luster between metallic luster and nonmetallic luster. Hurlbut
Said of the texture of an igneous rock in which the feldspar crystals are
approx. the same size as the pyroxene and are only partially included by
them. The term ophitic generally includes such textures. AGI
a. S. Afr. Rock that would have been the outcrop on the surface, but is
covered by other formations. Beerman
b. Area of intersection of a geologic feature with the surface of bedrock
beneath the regolith. Hawkes, 1
In coal and coke sampling, part of the sample consisting of a number of
increments spaced evenly over the unit. BS, 2
See:epigenetic
The sudden sinking or gradual downward settling of the Earth's surface
with little or no horizontal motion. The movement is not restricted in
rate, magnitude, or area involved. Subsidence may be caused by natural
geologic processes, such as solution, thawing, compaction, slow crustal
warping, or withdrawal of fluid lava from beneath a solid crust; or by
human activity, such as subsurface mining or the pumping of oil or
groundwater. See also:shift; cauldron subsidence; settlement.
Syn:land subsidence; bottom subsidence. AGI
The area affected by subsidence over areas where minerals or other
substances have been removed. The area is larger than the mined-out area
below. AGI