A muffle furnace for roasting ore out of contact with the products of
combustion. Standard, 2
Incipient joints.
A sublevel shaft, connected to the main (daylight to depth) shaft by a
transfer station. A winze. Pryor, 3
Scot. A side cutting without undercutting.
A vein that does not continue to the surface. See also:blind;
blind lode; blind lead. Fay
See:blind road
See:shadow zone
Echo trace on radar or sonar indicator screen. Hy
Massive, compact, fine-textured, fossiliferous gray sandstone ranging from
almost white to brown. It may be either Cambrian or Ordovician, or both,
at any given locality. It represents a period of slow intermittent
deposition of sandy material. Found in New Mexico and in Texas.
Hess
a. In quarrying, an unconfined charge of explosive used to bring down
dangerous ground that cannot be made safe by barring and that is too
inaccessible to bore. South Australia
b. A protrusion, more or less circular in plan, extending downward into a
coal seam. It represents the filling of a streambed pothole worn into the
upper surface of the coal-forming material. AGI
c. Copper as a smelter product before it is refined. Hoffman
d. A defect in metal, on or near the surface, resulting from the expansion
of gas in a subsurface zone. Very small blisters are called pinheads or
pepper blisters. ASM, 1
A wrought-iron bar impregnated with carbon by heating in charcoal. Used in
making crucible steel. CTD
An impure intermediate product in the refining of copper, produced by
blowing copper matte in a converter. ASM, 1
A reniform variety of chalcopyrite. Fay
Raw steel that has been cooled very slowly and that has a blistered
appearance. The blisters are formed by gas escaping from within the metal.
Camm
See:blower wax
The expansion of certain nonmetallic materials by heating until the
exterior of the particle or shape becomes sufficiently pyroplastic or
melted to entrap gases generated on the interior by the decomposition of
gas-producing components.
a. A division of a mine, usually bounded by workings but sometimes by
survey lines or other arbitrary limits.
b. A short piece of timber placed between the mine roof and the cap of a
timber set and directly over the cap support. A wedge driven between the
roof and the timber holds the set in place.
See also:blocking and wedging
c. A pillar or mass of ore exposed by underground workings.
See also:blocking out
d. Portion of an orebody blocked out by drives, raises, or winzes, so that
it is completely surrounded by passages and forms a rectangular panel. If
its character, volume, and assay grade are thus established beyond
reasonable doubt, it ranks as proved ore in the mine's assets.
Pryor, 3
e. The wedging of core or core fragments or the impaction of cuttings
inside a bit or core barrel, which prevents further entry of core into the
core barrel, thereby producing a condition wherein drilling must be
discontinued and the core barrel pulled and emptied to forestall loss of
core through grinding or the serious damage of the bit or core barrel.
See also:core block; plug. Long
f. An obstruction in a borehole. Long
g. See:sheave
A general term that refers to a mass mining system where the extraction of
the ore depends largely on the action of gravity. By removing a thin
horizontal layer at the mining level of the ore column, using standard
mining methods, the vertical support of the ore column above is removed
and the ore then caves by gravity. As broken ore is removed from the
mining level of the ore column, the ore above continues to break and cave
by gravity. The term "block caving" probably originated in the porphyry
copper mines, where the area to be mined was divided into rectangular
blocks that were mined in a checkerboard sequence with all the ore in a
block being removed before an adjacent block was mined. This sequence of
mining is no longer widely used. Today most mines use a panel system,
mining the panels sequentially or by establishing a large production area
and gradually moving it forward as the first area caved becomes exhausted.
The term "block caving" is used for all types of gravity caving methods.
There are three major systems of block caving, and they are differentiated
by the type of production equipment used. (1) The first system based on
the original block cave system is the grizzly or gravity system and is a
full gravity system wherein the ore from the drawpoints flows directly to
the transfer raises after sizing at the grizzly and then is gravity loaded
into ore cars. (2) The second system is the slusher system, which uses
slusher scrapers for the main production unit. (3) The last system is the
rubber-tired system, which uses load-haul-dump (LHD) units for the main
production unit. Block caving has the lowest cost of all mine exploitation
systems, with the exception of open pit mining or in situ recovery.
See also:top slicing
See:chute caving
Aust. A square mining claim whose boundaries are marked out by posts.
A plane figure representing a block of the Earth's crust (depicting
geologic and topographic features) in a three-dimensional perspective,
showing a surface area on top and including one or more (generally two)
vertical cross sections. The top of the block gives a bird's-eye view of
the ground surface, and its sides give the underlying geologic structure.
AGI