An obsolete term for blende. See also:sphalerite
A gate carried forward in the seam thickness only (which must be over 3 ft
or 0.9 m), with cut-throughs as required to the main gate. The false gate
has a short conveyor that takes the face conveyor coal and delivers it to
the main gate conveyor through a crosscut a short distance behind the
face. This layout enables the main gate rippings to be worked on three
shifts. Nelson
A laterally or vertically displaced, rather than indigenous, iron-oxide
zone. It may be confused with the iron oxide of a gossan, which is
weathered from underlying sulfide deposits. AGI
See:essonite
a. See:lazulite
b. Agate, jasper, or other varieties of chalcedony dyed blue.
Syn:false lapis lazuli; Swiss lapis; German lapis.
See:false lapis
Temporary arch legs used adjacent to the face conveyor in an advance gate
to allow the conveyor to be moved forward and still maintain the gate
supports. The conveyor side half-arch is temporarily replaced by props and
crossbars (false legs). When the conveyor has passed, the half-arch is
bolted back in position. Nelson
Some garnets, e.g., Arizona ruby, Bohemian ruby, Cape ruby, and some
spinels, e.g., balas ruby, ruby spinel, are ruby colored.
See also:balas ruby; Elie ruby.
An old term for cross-stratification. AGI
A stull so placed as to offer support or reinforcement for a stull, prop,
or other timber.
a. A transparent yellow variety of quartz, specif. citrine.
See also:citrine
b. A yellow variety of fluorite.
A tetragonal mineral, Cu3 SbS4 ; stannite group; occurs with
enargite, tetrahedrite-tennantite, chalcopyrite, and covellite in copper
ores worldwide, notably at Mankayan, Luzon, Philippines; Famatina,
Argentina; and Butte, MT.
The basic unit of the clan of igneous rocks. AGI
a. To drill a number of boreholes each in a different horizontal or
vertical direction from a single drill setup. Long
b. An accumulation of debris brought down by a stream descending through a
steep ravine and debouching in the plain beneath, where the detrital
material spreads out in the shape of a fan, forming a section of a very
low cone. See also:alluvial fan
Cleavage that, if studied over a large enough area, dips at different
angles so that, like the ribs of a fan, it converges either upward or
downward. AGI
A cut in which holes of equal or increasing length are drilled in a
pattern on a horizonal plane or in a selected stratum to break out a
considerable part of it before the rest of the round is fired; the holes
are fired in succession in accordance with the increasing angle they form
in relation to the face. BS, 12
A term applied to semiprecious stones prized for qualities other than
intrinsic value.
a. Soft coal from which all slack and nut coal has been removed.
Fay
b. Ark. Semianthracite coal of larger size than grate coal. Fay
a. The short tunnel connecting the upcast shaft with the exhaust fan.
See also:ventilation
b. The enclosed airtight passage, road, or gallery from the mine to the
fan. Mason
c. The passage or duct for the intake of a ventilating fan on a mine.
CTD
d. An airway leading from a mine shaft, or airway, to a fan. BS, 8
When there are two fans at a mine it is necessary to install isolation
doors for each drift leading to a fan in order to prevent the working fan
from drawing air from the outside atmosphere. With modern fan layouts, the
fan drift may be 5 m or more square and pass 300 m3 /s of air and
sometimes more. Modern fan drift doors can be fixed in any position from
fully open to fully closed and can be manipulated by one person from
outside the fan drift. Doors of the butterfly type are often used and can
be opened manually or by power. See also:main separation door