A hexagonal mineral, K2 Na6 Fe7 (SO4 ) (sub
12) O2 .18H2 O .
a. A fibrous serpentine mineral; a variety of chrysotile. AGI
b. See:micaceous sandstone
A tetragonal mineral, Cu(UO2 )2 (AsO4 )2 .8H
2 O ; meta-autunite group; grass to emerald green.
a. Iron of meteoric origin. AGI
b. An iron meteorite. AGI
a. A stone of meteoric origin; a stony meteorite. AGI
b. A meteorite having the appearance of a stone. AGI
Ground water of atmospheric origin.
A stony or metallic body that has fallen to the Earth's surface from outer
space. Adj: meteoritic.
a. An instrument, apparatus, or machine for measuring fluids, gases,
electric currents, etc., and recording the results obtained; e.g., a
gasmeter, a watermeter, or an air meter. Standard, 2
b. The fundamental unit of length in the metric system equal to 39.37079
in or 3.2808 ft. Standard, 2; Fay
A valve plunger that controls the rate of flow of a liquid or a gas.
Nichols, 1
CH4 ; carbureted hydrogen or marsh gas or combustible gases; formed
by the decomposition of organic matter. The most common gas found in coal
mines. It is a tasteless, colorless, nonpoisonous, and odorless gas; in
mines the presence of impurities may give it a peculiar smell. It weighs
less than air and may therefore form layers along the roof and occupy roof
cavities. Methane will not support life or combustion; with air, however,
it forms an explosive mixture, CH4 +2O2 -->CO2 .2H
2 O. The gases resulting from a methane explosion are irrespirable.
Methane is often referred to as combustible gases because it is the
principal gas composing a mixture that, when combined with proper
proportions of air, will explode when ignited. Breathing methane causes
ill effects only where the air is so heavily laden with it that oxygen is
supplanted. See also:colliery explosion; marsh gas; firedamp;
limits of flammability. Nelson; Webster 2nd; BCI
a. Capture of the concentrated methane through boreholes drilled into a
coalbed or associated strata. SME, 1
b. Outside the United States three main systems of methane drainage have
been developed: (1) the cross-measure borehole method, (2) the superjacent
roadway system and (3) the pack cavity system. The cross-measure borehole
method which consists of boring holes from 2-1/4 to 3-1/4 in (5.7 to 8.3
cm) in diameter and 150 to 300 ft (45 to 90 m) in length, into the strata
above or below the seam, generally close to the working face. This method
has the advantage of being suited to a wide variety of conditions and does
not require another seam within reasonable distance above or below the
seam to be drained, or the use of solid stowing
Syn:cross-measure borehole system
boreholes are drilled from a roadway situated above the seam being worked,
the drainage of the methane then taking place from this roadway. In the
pack cavity system, corridors are left and supported in the goaf as the
face advances, and from these combustible gases is drawn off.
Syn:combustible gases drainage; corridor system.
Sinclair, 1; Roberts, 1
c. In contrast to the above, methane drainage technology in the United
States is conducted from the surface as well as underground. Underground
methane drainage is primarily by means of horizontal boreholes drilled
into the coalbed to be extracted. Surface methane drainage methods include
vertical gob gas vent holes on longwall panels and hydraulically
stimulated vertical wells generally drilled several years in advance of
mining into virgin coalbeds.
A system whereby the methane content of the mine air is indicated
automatically at all times. When the content reaches a predetermined
concentration, the electric power is cut off automatically from each
machine in the affected area. The mechanism is so devised that its setting
cannot be altered. The system is used, mainly, in conjunction with the
operation of continuous miners and power loaders. Nelson
An instrument for detecting methane in mine air. It contains an electric
battery that sustains a small electric glow light. As soon as a certain
percentage of methane enters the workings, a tiny explosion occurs in the
fuse head, where a fine wire filament is melted and starts a bell ringing
continuously. Fay
An instrument that gives a continuous record of the methane concentration
over a period of time. Roberts, 1
A methane detector. See also:methanometer
A nonautomatic methane detector approved under the regulations for use in
coal mines. The instrument is normally calibrated at 1% methane, and this
provides an accuracy of + or -0.05% over the most important part of the
scale; i.e., 0.75% to 1.5%. It weighs 3-1/2 lb (1.6 kg), and the source of
power is an Edison cap lamp battery. Nelson
An instrument for determining the methane content in mine air.
See also:sampling instrument; catalytic methanometer. Nelson
See:bromoform
The system adopted to work or extract material in a mine. It includes all
the operations involved in the cutting, handling, and transport of
valuable material and waste rock, support of ground, ventilation of
workings, and provision of supplies. The term does not include winding or
hoisting, surface handling, and preparation or dressing.
See also:coal mining methods
A study to provide the essential data on which mine management can operate
in making the most effective use of workpower, machines, and materials.
Method study has been applied in the mining industry for many years,
although sometimes under different names. See also:time study;
work study. Nelson