a. A mass of rock, coal, or ore that has collapsed from the roof or sides
of a mine roadway or face. Falls of ground are responsible for the
greatest proportion of underground deaths and injuries. Nelson
b. A length of face undergoing holing or breaking down for loading.
c. The rolling of coal from the face into the room, usually as the result
of blasting; sometimes the amount blasted down. Locally, also the caved
roof after the coal is extracted. BCI
d. To blast, wedge, or in any other way to break down coal from the face
of a working place. CTD
e. A system of working a thick seam of coal by falling or breaking down
the upper part after the lower portion has been mined.
CF:caving system
f. A mass of roof or side that has fallen in any subterranean working or
gallery, resulting from any cause whatever.
g. The collapse of the roof of a level or tunnel, or of a flat working
place or stall; the collapse of the hanging wall of an inclined working
place or stope. CTD
h. To crumble or break up from exposure to the weather; clays, shales,
etc., fall.
Movable supports for a cage. Also called fangs; keps. Nelson
A test used to determine impact sensitivity of an explosive conducted by
allowing standard hammer weights to fall on an amount of confined
explosive charge and measuring the fall height required to decompose or
detonate the charge. Meyer
A soil permeability test in which the borehole is filled up with water and
the rate at which the water falls is observed. Mining
A limit recorder of the intensity of ground vibrations initiated by a
quarry or opencast blast. It consists essentially of a level glass base on
which a number of pins 1/4 in (0.64 cm) in diameter and of lengths ranging
from 6 to 15 in (15 to 38 cm) are stood upright. The pins stand inside
hollow steel rods so that each pin can fall over independently of the
others. The longer the pin, the less energy required to topple it. In
practice it has been accepted that if the shorter pins (up to 10 in or 25
cm) remain standing, then there is no possibility of structural damage to
a building by a quarry blast. See also:vibrograph
Blast furnace slag that contains sufficient calcium orthosilicate to
render it liable to fall to a powder when cold. Such a slag is precluded
from use as a concrete aggregate by the limits of composition specified in
British Standards 1047. Dodd
An imaginary line or narrow zone connecting the waterfalls on several
adjacent near-parallel rivers, marking the points where these rivers make
a sudden descent from an upland to a lowland, as at the edge of a plateau;
specif. the fall line marking the boundary between the ancient, resistant
crystalline rocks of the Piedmont Plateau and the younger, softer
sediments of the Atlantic Coastal Plain in the Eastern United States. It
also marks the limit of navigability of the rivers. Syn:fall zone
AGI
Rock falling from the roof into a mine opening. See also:fall
Weed, 2
See:bordroom man
A hinged platform to cover the mouth of a shaft. Nelson
See:fall line
An early name for violet-colored fluorite when cut as a gem. Other colors
of the same mineral were called false emerald, ruby, sapphire, or topaz.
Fay
An anticlinelike structure produced by compaction of sediment over a
resistant mass, such as a buried hill or reef. AGI
See:crossbedding; current bedding.
a. An apparent bedrock underlying an alluvial deposit that conceals a
lower alluvial deposit; e.g., a bed of clay or sand cemented by hydrous
iron oxides, on which a gold placer deposit accumulates, and under which
there is another alluvial deposit resting on bedrock. AGI
b. A strip of wire screening nailed to a wooden frame that fits into the
bottom of a sluice box to trap fine sand containing gold. When the frame
is removed, the fine sand, containing gold, is scraped up and placed in
pans for washing down. False bottoms are employed for saving both fine and
coarse gold. Griffith
c. Aust.; U.S. A bed of drift lying on the top of other alluvial deposits,
beneath which there may be a true bottom or a lower bed of wash resting
directly upon the bedrock. Fay
d. A floor of iron placed in a puddling machine. Fay
e. A flat, hexagonal or cylindrical piece of iron upon which the ore is
crushed in a stamp mill; the die. In Victoria, Australia, it is called
stamper bed. Fay
f. An insert put in either member of a die set to increase the strength
and improve the life of the die. ASM, 1
See:moldavite
a. See:strain-slip cleavage
b. A secondary cleavage superposed on slaty cleavage.
c. Closely spaced surfaces, a millimeter or so apart, along which a rock
splits. The surfaces are either minute faults or the short limbs of small
folds. AGI
d. A quarrying term for minor cleavage in a rock, such as slip cleavage,
to distinguish it from the dominant cleavage. Geologically, the term is
misleading and should be avoided. AGI
Any colorless mineral that if cut and polished makes a brilliant gem;
e.g., zircon, corundum, and topaz. Having less dispersion, lower
refractive index, and birefringence, they are easily distinguished from
diamond.
The growth of a metastable or monotropic phase under conditions apparently
indicating true equilibrium, as in the development of andalusite crystals
in which sillimanite actually represents the stable phase. AGI
See:pseudomorph