| Main entry - A main haulage
road. |
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| Main fan - A mechanical
ventilator installed at the surface; operates by either exhausting or blowing to induce
airflow through the mine roadways and workings. |
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| Manhole - A safety hole
constructed in the side of a gangway, tunnel, or slope in which miner can be safe from
passing locomotives and car. Also called a refuge hole. |
|
| Man trip - A carrier of mine
personnel, by rail or rubber tire, to and from the work area |
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| Manway - An entry used
exclusively for personnel to travel form the shaft bottom or drift mouth to the working
section; it is always on the intake air side in gassy mines. Also, a small passage at one
side or both sides of a breast, used as a traveling way for the miner, and sometimes, as
an airway, or chute, or both. |
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| Meridian -– A surveying
term that establishes a line of reference. The bearing is used to designate direction. The
bearing of a line is the acute horizontal angle between the meridian and the line.
Azimuths are angles measured clockwise from any meridian. |
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| Methane – A potentially
explosive gas formed naturally from the decay of vegetative matter, similar to that which
formed coal. Methane, which is the principal component of natural gas, is frequently
encountered in underground coal mining operations and is kept within safe limits through
the use of extensive mine ventilation systems. |
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| Methane monitor - An
electronic instrument often mounted on a piece of mining equipment, that detects and
measures the methane content of mine air. |
|
| Milling ore - ore that must be
concentrated at or near the mine before it is shipped. |
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| Mine development - The term
employed to designate the operations involved in preparing a mine for ore extraction.
These operations include tunneling, sinking, cross-cutting, drifting, and raising. |
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| Miner - One who is engaged in
the business or occupation of extracting ore, coal, precious substances, or other natural
materials from the earth's crust. |
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| Mineral - An inorganic
compound occurring naturally in the earth's crust, with a distinctive set of physical
properties, and a definite chemical composition. |
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| Mining Engineer - A person
qualified by education, training, and experience in mining engineering. A trained engineer
with knowledge of the science, economics, and arts of mineral location, extraction,
concentration and sale, and the administrative and financial problems of practical
importance in connection with the profitable conduct of mining. |
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| Misfire - The complete or
partial failure of a blasting charge to explode as planned. |
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| MSHA - Mine Safety and Health
Administration; the federal agency which regulates coal mine health and safety. |
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| Muck - a common term for any
broken ore or waste underground. |
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| Mud cap - A charge of high
explosive fired in contact with the surface of a rock after being covered with a quantity
of wet mud, wet earth, or sand, without any borehole being used. Also termed adobe, dobie,
and sandblast (illegal in coal mining). |
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