Appendix:Dictionary of Mining, Mineral, and Related Terms/M/1

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See: macle.


Crushed stone of regular sizes below 3 in (7.6 cm) for road construction, commonly with tar or asphalt binder. The sizes below 1 in (2.54 cm) are more specif. defined as chippings. See also: penetration macadam; tarmacadam.

MacArthur and Forest cyanide process

A process for recovering gold by leaching the pulped gold ore with a solution of 0.2% to 0.8% potassium cyanide, KCN, and then with water. The gold is obtained from this solution by precipitation on zinc or aluminum, or by electrolysis. See also: Elsner's equation.


a. A tetragonal mineral, PbTiO (sub 3) ; black; in irregular grains in quartz-syenite veins near Prilep, Macedonia.

b. A bluish-black aphanitic igneous rock composed of alkali feldspars and biopyriboles; related to mugearite, a trachyandesite, Macedon district, Victoria, Australia. The name is not part of the IUGS classification of extrusive igneous rocks.


Applied to all petrologic units seen in microscopic sections of coal, as distinct from the visible units seen in the hand specimens. Comparable in rank to mineral as used in petrography. Thus, macerals are organic units composing the coal mass, being the descriptive equivalent of the inorganic units composing rock masses and universally called minerals. Individual macerals have the termination -inite; i.e., vitrinite, as the organic unit making up the lithologic specimen, vitrain. Three groups are recognized: (1) vitrinites; (2) exinites; and (3) inertinites.


A silver ore consisting of a mixture of sulfides, arsenides, etc., and containing cobalt, nickel, and lead. CF: animikite.


See: mcgovernite.

machine boss

In bituminous coal mining, a foreperson who is in charge of machine workers who undercut the working face of coal prior to blasting, and machine loaders who load the coal into cars after it is blasted down.

machine cut

A slot or groove made horizontally or vertically in a coal seam by a coal cutter, as a preliminary step to shot firing. See also: cutting horizon.

machine-cutter helper

See: machine helper.


a. A smooth surface finish on metal.

b. Shaped by cutting or grinding.

machine design

The application of scientific principles to the practical constructive art of engineering, with the object of expressing original ideas in the form of drawings. See also: theory of machines.

machine driller

In mining, one who operates any one of several types of heavy, mounted or unmounted, compressed-air drilling machines to drill holes into the working face of ore or rock into which explosives are inserted and set off to blast down the mass. Also called drill engineer; drillman; drill operator; power driller.

machine helper

In anthracite and bituminous coal mining, one who assists the machineman in moving and setting up the coal-cutting machine in position for cutting a channel under or along the sides of the coal working face prior to breaking the coal down with explosives. Also called chain-machine helper; coal-cutter helper; cutter helper; cutting-machineman helper; jack setter; machine-cutter helper; machineman helper; miner; assistant; mining-machine-operator helper.

machine holings

The small coal or dirt produced by a coal cutter.

machine loader

a. In anthracite and bituminous coal mining, person who operates an electric loading machine that digs, elevates, and loads coal blasted from the working face into cars by means of a conveyor loaded by a scraping device, a digging conveyor, or a shoveling mechanism. May be designated according to machine used, as Joy loader. Also called loader engineer; loader operator; loader runner; loading-machine man; loading-machine operator; loading-machine runner.

b. Machine loader I is used in anthracite coal mining, bituminous coal mining, and metal mining, to designate one who operates a small electric or air-power shovel in underground working places to load ore or rock into cars after it has been blasted from the working face. Also called loader operator; loading-machine operator; mechanical-shovel operator; shovel operator. c. Machine loader II is used in anthracite coal mining, bituminous coal mining, and metal mining, to designate one who operates a loading machine consisting of a small hoisting engine and a cable-drawn scraper, or scoop, to load ore or rock into cars after it has been blasted from the working face in underground or open-pit mines. Also called scraper-loader hoistman; scraper-loader operator; scraper operator.

machine loader helper

In anthracite coal mining and bituminous coal mining, a laborer who assists a machine loader in loading coal into cars.


a. A coal-cutter operator. See also: coal-cutter team.

b. A person who sets up and operates an electrically driven or compressed-air-driven coal-cutting machine that is used to cut out a channel along the bottom or side of the working face of coal so that it may be blasted down without shattering the mass. Also called coal cutter; coal-cutting machine operator; machine cutter; cutter operator; cutting machine operator; holer; undercutter. c. Eng. One who weighs coal, etc., and keeps an account of the number of cars sent to the surface.

machineman helper

See: machine helper.

machine miner

In bituminous coal mining, a general term applied to workers who are capable of operating one or more coal mining machines used for drilling, loading, and undercutting. Usually designated as machine driller; machine loader I; machine loader II; machineman. Also called machine operator; machine runner; mining machine operator.

machine mines

Mines in which coal is cut by machines.

machine mining

a. Implies the use of power machines and equipment in the excavation and extraction of coal or ore. In coal mines, the term almost invariably signifies the use of coal cutters and conveyors and perhaps some type of power loader working in conjunction with face conveyors. See also: face mechanization.

b. Mechanized mining.

machine nog

Eng. A wedge-shaped wood block for supporting machine-cut coal.

machine operator

See: machine miner.

machine rating

a. The amount of power a machine can deliver without overheating.

b. Also, work capacity of a machine.

machine runner

See: machine miner.

machine screw

A very commonly used type of screw with clear-cut threads and of a variety of head shapes. It may be used either with or without a nut.

machine set

See: mechanical set.

machine sumper

See: sumper.

machine tool

Any machine used for cutting metal, such as a boring machine, drill, grinder, planing machine, hobber, shaper, or lathe.

machine wall

The face at which a coal-cutting machine works.


Aust. The person in charge of a coal cutter.


See: thorogummite.

Mac-Lane system

This system consists essentially of an inclined rail track with the haulage gear and the loading station at the base. The haulage rope passes round a return sheave in the extending frame at the top of the heap. The tipping gear may consist of a carriage with a portable tippler that conveys a tub of dirt to the top of the heap, where a trigger operates the tippler, thus discharging the tub. For a greater quantity, the carriage incorporates a revolving frame carrying two or three tubs; this gives a broader top to the heap. The main disadvantages of this system are the unsightly conical heaps produced and the tendency to segregation of material, with the large pieces at the base of the heap, which increases the danger of spontaneous combustion.


a. A twin crystal; esp. octahedral diamond twins flattened parallel to the twin plane. Also spelled maacle, maccle, mackle.

b. A variety of andalusite with tessellated cross section resulting from segregation of carbonaceous impurities. Syn: chiastolite.

Maclean separator

A revolving disk-type magnetic separator widely used for the separation of large quantities of ilmenite from tin ore.


a. Twinned.

b. See: tessellated. c. Spotted. Also spelled mackled.


A prefix meaning large, long; visibly large, e.g., macrocrystalline. CF: micro-. Syn: mega-.


In the orthorhombic and triclinic systems, an obsolete term for the longer lateral crystallographic axis, the b axis in orthorhombic and mostly the b axis in triclinic minerals.


Said of the texture of a rock consisting of or having crystals that are large enough to be distinctly visible to the unaided eye or with the use of a simple lens; also, said of a rock with such a texture. Syn: eucrystalline. See also: macromeritic; phaneritic.


In crystallography, the longer lateral axis in the orthorhombic and triclinic systems.


a. In crystallography, a dome parallel to the macrodiagonal. CF: dome.

b. In the orthorhombic system, an obsolete term for a form of four faces parallel to the macro-axis, but intercepting the other two. Syn: horizontal prism. c. In the triclinic system, an obsolete term for a form of two faces parallel to the macro-axis, but intercepting the other two.


Etching of a metal surface for accentuation of gross structural details and defects for observation by the unaided eye or at magnifications not exceeding 10 diameters.


A graphic reproduction of the surface of a prepared specimen at a magnification not exceeding 10 diameters. When photographed, the reproduction is known as a photomacrograph.


See: phaneritic.


Porosity visible without the aid of a microscope, such as pipes and blowholes in ingots.


a. Visible at magnifications of from 1 to 10 diameters.

b. Visible without a microscope or in a hand specimen. See also: megascopic. CF: microscopic.


a. The general arrangement of crystals in a solid metal (for example, an ingot) as seen by the naked eye or at low magnification. The term is also applied to the general distribution of impurities in a mass of metal as seen by the naked eye after certain methods of etching.

b. The structure of metals as revealed by examination of the etched surface of a polished specimen at a magnification not exceeding 10 diameters. c. A structural feature of a rock that is discernible to the unaided eye, or with the help of a simple magnifier. d. The arrangement of crystals in a metal or in a rock that, with or without etching or other chemical treatment, is discernible to the unaided eye or with the help of a simple magnifier (generally less than 10X).


Applied to the group of contact-metamorphic rocks represented by spotted slates, to denote its spotted or knotted character. The term may be applied either to the rock or to its structures. See also: spotted slate.

maculose rock

See: spotted slate.

Madagascar aquamarine

A strongly dichroic variety of blue beryl obtained, as a gemstone material, from Malagasy Republic.

Madaras system

A method of obtaining pig iron, consisting of charging a retort with a mixture of iron ore, coal, and enough water to form a paste; and injecting compressed air at 2 to 4.2 kg/cm (super 2) pressure and at 815 to 930 degrees C to burn the coal. In a few minutes the entire mineral charge is heated to 980 to 1,095 degrees C, which is the optimum range for hydrogen reduction; then hydrogen is injected at a temperature of 815 to 923 degrees C at 2 to 8 kg/cm (super 2) pressure so that it penetrates the entire mass and reacts with the iron oxide to produce steam and metallic iron. About 50% of the injected hydrogen reacts with the ore to produce sponge iron. Sulfur is oxidized by the hot air and is eliminated by the hydrogen.

made ground

a. A recent deposit, as of river silt.

b. Ground formed by filling in natural or artificial pits with hardcore or rubbish.

Madeira topaz

Citrine variety of quartz. CF: false topaz; Spanish topaz.

made up

Coupled; the assembled component parts of a drill string or pipe system.


A plot of mean absolute difference of paired sample measurements as a function of distance and direction. Madograms are not true variograms, and generally should not be used in kriging. If used, the kriged estimates might be "reasonable," but the kriging standard deviations will be meaningless.

madrepore marble

A fossiliferous limestone occurring in a variety of colors. It takes a high polish, is used as a marble, and derives its name from its most characteristic fossil, a species of coral.


An intrusive trachytic rock, regarded as a differentiation product of a gabbroic magma. Maenite is a bostonite relatively high in calcium and low in potassium.


Said of igneous rocks containing roughly equal amounts of felsic and mafic minerals, color index 40 to 70.


Pertaining to or composed dominantly of the ferromagnesian rock-forming silicates; said of some igneous rocks and their constituent minerals. CF: basic; felsic. See also: mafite.

mafic front

See: basic front.


Any dark mineral in Johannsen's classification of igneous rocks. See also: mafic.


a. A storage place for explosives.

b. A building specially constructed and located for the storage of explosives. CF: powder chest.


An isometric mineral, gamma-Fe (sub 2) O (sub 3) ; magnetite series; spinel group; dimorphous with hematite; strongly ferrimagnetic. Syn: oxymagnite.


Roasted copper pyrites.


Naturally occurring molten rock, generated within the Earth and capable of intrusion and extrusion, from which igneous rocks are derived through solidification and related processes. It may or may not contain suspended solids (such as crystals and rock fragments) and/or gas phases. Adj: magmatic.


Of, pertaining to, or derived from magma. See also: igneous.

magmatic assimilation

See: assimilation.

magmatic blister

The swelling up by differential heating of magma; e.g., by local concentrations of radioactive matter.

magmatic corrosion

A process of re-solution in which an early formed phase, such a quartz phenocryst, later becomes corroded or embayed as the result of some change in the conditions affecting the solubility of the phase; sometimes corrosion rims result. Syn: corrosion.

magmatic cycle

See: igneous cycle.

magmatic deposit

See: magmatic ore deposit.

magmatic differentiation

The process by which more than one rock type is derived from a parent magma. CF: assimilation. Syn: differentiation.

magmatic disseminated ore deposit

See: disseminated deposit.

magmatic dissolution

See: assimilation.

magmatic injection deposit

Straight magmatic mineral (ore) deposit, the formation of which has often been ascribed to injection into the older country rock of liquefied crystal differentiates, of residual liquid segregations, or of immiscible liquid separations and accumulations. An older term.

magmatic ore deposit

An ore deposit formed by magmatic segregation, generally in mafic rocks and layered intrusions, as crystals of metallic oxides or from an immiscible sulfide liquid. Syn: magmatic deposit.

magmatic segregation

Concentration of crystals of a particular mineral (or minerals) in certain parts of a magma during its cooling and crystallization. Some ore deposits (i.e., magmatic ore deposits) are formed in this way. See also: differentiation.

magmatic stoping

A process of magmatic emplacement or intrusion that involves detaching and engulfing pieces of the country rock. The engulfed material presumably sinks downward and/or is assimilated. See also: piecemeal stoping.

magmatic water

Water contained in or expelled from magma. CF: juvenile water.


One who believes that much granite is a primary igneous rock produced by differentiation from basaltic magma. CF: transformist.


Trademark for iron oxide heavy media systems for the purification of coal, sand, gravel, and other similar materials.


A widely used medium for magnetic recording. It consists of a circular platter of magnetically coated plastic material that rotates on a turntable in the same way as a phonograph record. The magnetic channels, each in contact with a fixed head aligned along a radius from the center, are on concentric circular bands extending inward from the outer edge of the disk.


Magnesium oxide, MgO. A constituent of lime made from dolomitic limestone.

magnesia alum

See: pickeringite.

magnesia covering

Hydrated magnesium carbonate containing about 15% asbestos, used for heat insulation. Also referred to as 85% magnesia.

magnesia glass

Glass containing usually 3% to 4% of magnesium oxide. Electric lamp bulbs have been mainly made from this type of glass since fully automatic methods of production were adopted.

magnesia mica

See: biotite.

magnesian hornfels

A fine-grained metamorphic rock derived from a high-magnesium igneous rock; e.g., serpentine. See also: hornfels.

magnesian limestone

A limestone containing from 5% to 35% MgCO (sub 3) . CF: dolomitic limestone.

magnesian marble

A crystalline variety of limestone containing not less than 5% nor more than 40% of magnesium carbonate as the dolomite constituent.

magnesian schist

A schistose metamorphic rock derived from a rock high in content of magnesium; e.g., serpentine. See also: schist.

magnesian spar

See: dolomite.

magnesia ramming materials

Granular, airsetting mixtures, containing 70% to 80% MgO, used for monolithic furnace linings.


An isometric mineral, MgCr (sub 2) O (sub 4) ; chromite series; spinel group; forms series with spinel and with chromite; crystallizes in black octahedra, but commonly massive. Also spelled magnochromite. Syn: picrochromite.


An isometric mineral, MgFe (sub 2) O (sub 4) ; magnetite series; spinel group; strongly ferrimagnetic. Also spelled magnoferrite.


A magnesian variety of laumontite.


A trigonal mineral, MgCO (sub 3) ; calcite group; rhombohedral cleavage; in veins in serpentinite and peridotite, magnesium-rich schist, and altered dolomitic marbles. Syn: giobertite; magnesium carbonate.

magnesite cement

Common term for ground magnesite.

magnesite refractory

A refractory material, fired or chemically bonded, consisting essentially of dead-burned magnesite; the MgO content usually exceeds 80%. Such refractories are used in the hearths and walls of basic steel furnaces, mixer furnaces, and cement kilns.


A light, silvery-white, and fairly tough metal. Symbol, Mg. It does not occur uncombined, is found in large deposits in the form of magnesite, dolomite, and other minerals. Readily ignites upon heating. Used in flashlight photography, flares, and pyrotechnics, including incendiary bombs. Its alloys are essential for airplane and missile construction.

magnesium aluminate

MgAl (sub 2) O (sub 4) ; melting point, 2,135 degrees C; sp gr, 3.6; thermal expansion (100 to 1,000 degrees C), 9.0 X 10 (super -6) . This compound is the type mineral of the spinel group. See also: spinel.

magnesium-aluminum garnet

See: pyrope.

magnesium bentonite

A smectite with exchangeable magnesium.

magnesium blodite

See: bloedite.

magnesium carbonate

See: magnesite.

magnesium chalcanthite

See: pentahydrite.


A monoclinic mineral, (Mg,Mn) (sub 3) Zn (sub 2) (AsO (sub 4) )(OH,O) (sub 6) ; associated with manganese silicates at Franklin, NJ.

magnesium front

See: basic front.

magnesium kaolinite

See: amesite.

magnesium leonite

See: leonite.

magnesium mica

See: phlogopite.

magnesium minerals

Chiefly magnesite, dolomite, and brucite.

magnesium orthite

A magnesian variety of allanite.

magnesium titanate

MgTiO (sub 3) . Used in ceramic dielectric bodies. Although relatively low in dielectric constant, it has a positive temperature coefficient of capacity. Thus, it can be used in conjunction with a negative coefficient material; e.g., titania, to produce a near 0 temperature coefficient product.

magnesium zirconate

MgZrO; melting point, 2,150 degrees C. This compound is sometimes added in small amounts (up to 5%) to other electroceramic bodies to lower their dielectric constant at the Curie point.


Of or pertaining to a mineral, object, area, or locale possessing the properties of a magnet.

magnetic alloys

Alnico is an alloy of aluminum, nickel, and cobalt, with strong magnetic properties similar in all directions. Alcomax is anisotropic, with maximum flux along preferred axis. Hycomax is also anisotropic. Platinax, a cobalt-platinum alloy containing 23.3% cobalt, is isotropic.

magnetic anomaly

Variation of the measured magnetic pattern from a theoretical or empirically smoothed magnetic field.

magnetic azimuth

The azimuth measured clockwise from magnetic north through 360 degrees ; the angle at the point of observation between the vertical plane through the observed object and the vertical plane in which a freely suspended magnetized needle, influenced by no transient artificial magnetic disturbance, will come to rest.

magnetic bearing

The bearing expressed as a horizontal angle between the local magnetic meridian and a line on the Earth; a bearing measured clockwise from magnetic north. It differs from a true bearing by the amount of magnetic declination at the point of observation.

magnetic bort

See: bort.

magnetic bottle

A magnetic field used to confine a plasma in controlled-fusion experiments.

magnetic circuit

The closed path taken by the magnetic flux in an electric machine or other piece of apparatus.

magnetic clutch

One in which connection between drive and driven member is provided by electromagnetic force.

magnetic correlation

The orientation of an underground survey, using the Earth's magnetic field.

magnetic crack detection

The part to be examined is magnetized either by passing a heavy current through it or by making it the core of a coil through which a heavy current is passed. Small cracks, or nonmagnetic phases such as inclusions, cause the magnetic flux to break the surface, thus forming small magnets. When the part is sprayed with a suspension of iron oxide particles in paraffin, the particles cling to the small magnets and thereby reveal defects.

magnetic declination

In nautical and aeronautical navigation, the continually changing acute angle between the direction of the magnetic and geographic meridians. The term "magnetic variation" is preferred.

magnetic detector

An electrical device for indicating the presence of magnetic material in an area.

magnetic dip

Vertical angle through which a freely suspended magnetic needle dips from horizontal.

magnetic domain

Aggregation of ferromagnetic atoms into a group, usually a fraction of a micrometer in size, which lies among similar groups with random group orientation. This cancels out any magnetic moment until or unless they all are oriented by an applied magnetic field.

magnetic elements

a. These are declination, dip, and magnetic intensity in the horizontal plane.

b. The characteristics of a magnetic field that can be expressed numerically. The seven magnetic elements are declination D, inclination I, total intensity F, horizontal intensity H, vertical intensity Z, north component X, east component Y. Typically, only three elements are needed to give a complete vector specification of the magnetic field.

magnetic feeder

Any feeder that uses magnetism to pick up, hold, separate, and deliver objects.

magnetic field

a. Space surrounding a magnet or current-carrying coil, in which appreciable magnetic force exists. Its intensity (H) is the force exerted on a unit pole.

b. A region in which magnetic forces would be exerted on any magnetized bodies or electric currents present; the region of influence of a magnetized body or an electric current.

magnetic field strength

The force exerted on a unit pole is the field strength at that point.

magnetic flocculation

Phenomenon that results from residual magnetism of ferromagnetic particles that have bunched together under the influence of their individual polar forces.

magnetic flowmeter

A device used for the flow measurement of abrasive slurries. The calibration is affected by the presence of magnetic constituents in the slurry, and therefore, a pipe coil is also used to compensate the magnetic flowmeter calibration for varying amounts of magnetic material in the slurry.

magnetic flux

a. Induced strength or flux density in a magnetic field, measured in maxwells: B = 4pi /A + H, where B = the flux density, P = the strength of each magnetic pole, A = the cross-sectional area of a cylinder through which the flux flows, and H = the magnetic intensity in oersteds. See also: magnetic intensity.

b. The surface area times the normal component of magnetic induction B; the number of magnetic field lines crossing the surface of a given area. Expressed in maxwells in the cgs system.

magnetic gradiometer

An instrument, designed but not applied, for measuring the gradient of the magnetic intensity.

magnetic hoist

A hoisting device that does its lifting by means of an electromagnet.

magnetic hysteresis

See: hysteresis.

magnetic induction

a. Magnetic-flux density, symbolized by B. In a magnetic medium, it is the vector sum of the inducing field H and the magnetization M. B is expressed in teslas in SI and in gauss or gammas in the cgs system. Syn: magnetic field.

b. In a magnetic medium, the vector sum of the inducing field H and the corresponding intensity of magnetization I, according to the relationship B = H + 4pi I. c. A nonrecommended syn. of electromagnetic induction. d. The process of magnetizing a body by applying a magnetic field. This usage is not recommended.

magnetic intensity

A vector quantity pertaining to the condition at any point under magnetic influence (as of a magnet, an electric current, or an electromagnetic wave) measured by the force exerted in a vacuum upon a free unit north pole placed at the point in question. Also called magnetic force.

magnetic iron ore

See: magnetite.

magnetic level coil

A device for measuring the liquid level in sumps and other vessels. It consists of a loop of wire that is encased in a fiber glass protective sheath. The loop is inserted in a sump of thickener containing a magnetite or ferrosilicon slurry, and the electrical signal given off represents the level of the slurry surrounding the loop.

magnetic meridian

The horizontal line that is oriented, at any specified point on the Earth's surface, along the direction of the horizontal component of the Earth's magnetic field at that point; not to be confused with isogonic line. Syn: geomagnetic meridian.

magnetic method

A geophysical prospecting method that maps variations in the magnetic field of the Earth that are attributable to changes of structure or magnetic susceptibility in certain near-surface rocks. Sedimentary rocks generally have a very small susceptibility compared with igneous or metamorphic rocks, and most magnetic surveys are designed to map structure on or within the basement, or to detect magnetic minerals directly. Most magnetic prospecting is now carried on with airborne instruments.

magnetic mirror

A magnetic field used in controlled-fusion experiments to reflect charged particles back into the central region of a magnetic bottle.

magnetic moment

a. That vector associated with a magnetized mass; the vector product of it and the magnetic field intensity in which the mass is immersed (ignoring the field distortion thereby produced) is a measure of the resulting torque. Also called moment of a magnet.

b. A vector quantity characteristic of a magnetized body or an electric-current system; it is proportional to the magnetic-field intensity produced by this body and also to the force experienced in the magnetic field of another magnetized body or electric current. The magnetic moment per unit volume is the magnetization.

magnetic permeability

Ratio of magnetic induction (B) to the inducing field of magnetic intensity (H). With magnetic intensity lines of force per square centimeter in air, and flux density lines in a substance placed in that field, B/H is the magnetic permeability. When this is less than 1.0, the substance is diamagnetic; above 1.0, paramagnetic; and when high, ferromagnetic.

magnetic plug

A drain or inspection plug magnetized for the purpose of attracting and holding iron or steel particles in a lubricant.

magnetic polarity

The orientation of the constituent minerals within the rocks of the Earth's crust conforming to the Earth's magnetic field as it existed at the time the strata were deposited. See also: core orientation.

magnetic pole

a. Either of two points on the Earth's surface where the lines of magnetic force are vertical; an end of the axis of the Earth's magnetic polarity, not coincident with a geographic pole, and continually changing its position. The north magnetic pole is in northern Canada.

b. Either of two nonstationary regions on the Earth that sometimes move many miles in a day, toward which the isogonic lines converge, and at which the dip is + or -90 degrees . c. The area on a magnetized part at which the magnetic field leaves or enters the part. It is a point of maximum attraction in a magnet.

magnetic prospecting

See: magnetic method.

magnetic pyrite

See: pyrrhotite.

magnetic recording

Any process by which the output of a detector-amplifier system is recorded on a magnetic recording medium. The advantages of such a system are that the resulting records may be played back and converted into conventional records with phase shifting, mixing, etc., between traces and with filtering variations. Most modern magnetic recording is in digital form.

magnetic roasting process

Heating ferrous iron ore in the presence of air in order to oxidize the iron content, present in whatever form, to the magnetic oxide so that in a subsequent operation it can be separated from the gangue by means of a magnetic separator. Also, roasting a hematitic ore with scrap iron to reduce it to magnetite.

magnetic roll feeder

A feeder that uses magnetized, power-operated rolls for separating and delivering objects.


Branch of science that deals with magnetic phenomena.

magnetic separation

a. The separation of magnetic materials from nonmagnetic materials, using a magnet. This is an esp. important process in the beneficiation of iron ores in which the magnetic mineral is separated from nonmagnetic material; e.g., magnetite from other minerals, roasted pyrite from sphalerite, etc.

b. The use of permanent magnets or electromagnets to remove relatively strongly ferromagnetic particles from paramagnetic and diamagnetic ores.

magnetic separator

a. A device used to separate magnetic from less magnetic or nonmagnetic materials. The crushed material is conveyed on a belt past a magnet.

b. For medium solids recovery. A device in which medium solids are caused to adhere, by magnetic means, to a conveying belt or drum, while a current of water removes nonmagnetic particles that contaminate the medium.

magnetic storm

A worldwide disturbance of the Earth's magnetic field, commonly with amplitude of 50 to 200 gammas. It generally lasts several days, and is thought to be caused by charged particles ejected by solar flares. Magnetic prospecting usually has to be suspended during such periods.

magnetic susceptibility

A measure of the degree to which a substance is attracted to a magnet; the ratio of the intensity of magnetization to the magnetic field strength. See: susceptibility.

magnetic unit in prospecting

The gamma (Gamma ), which equals 10 (super -5) Oe (7.9577 X 10 (super -4) A/m).

magnetic variation

See: declination.

magnetic variometer

A geophysical instrument similar to the gravimeter in that absolute values are not measured, but only the differences in vertical magnetic force between field stations and a selected base station.


a. That property of iron, steel, and some other substances, by virtue of which they exert forces of attraction and repulsion according to fixed laws.

b. The science that is concerned with the conditions and laws of magnetic force.


a. An isometric mineral, 8[FeOFe (sub 2) O (sub 3) ] ; spinel group; forms series with jacobsite and with magnesioferrite; crystallizes in octahedra; metallic; black; strongly ferrimagnetic; an accessory mineral in many igneous rocks; a common detrital mineral; a major mineral in banded iron formations and magmatic iron deposits; an ore of iron. Syn: black iron ore; lodestone; magnetic iron ore; octahedral iron ore. See also: iron ore.

b. The mineral series magnesioferrite, magnetite, maghemite, franklinite, jacobsite, and trevorite in the spinel group. Syn: iron series.


An igneous rock consisting essentially of magnetite and having an iron content of 65% to 70% or more. Apatite may accompany the magnetite.

magnetite olivinite

A dunite high in content of titaniferous magnetite and containing shreds of biotite.

magnetite spinellite

An eruptive iron ore occurring at Routivara, Sweden, and consisting of magnetite (in part titaniferous), spinel, and smaller amounts of olivine, pyroxene, apatite, and pyrrhotite. The ore contains about 14% titanic oxide.


A body is said to be magnetized when it possesses or can be made to possess that peculiar property whereby, under certain circumstances, it will naturally attract or repel a similar body in accordance with magnetic laws; e.g., drill rods become magnetized in use and will strongly attract other iron or steel articles.

magnetizing force

a. The phenomenon associated with a magnetic flux density at a point. Theoretically, measured by the mechanical force on a unit magnetic pole in an evacuated tunnel along the direction of the magnetic flux; the magnetomotive force per centimeter in this direction.

b. A force field, resulting from the flow of electric currents or from magnetized bodies, that produces magnetic induction.

magnetizing roast

A process in which an ore containing pyrite is heated and the magnetic iron oxide so formed is removed by a magnetic separator. In many cases the iron oxide is extracted as gangue.


a. An instrument for measuring magnetic intensity. In ground magnetic prospecting, an instrument for measuring the vertical magnetic intensity; in airborne magnetic prospecting, an instrument for measuring the total magnetic intensity. Also, an instrument used in magnetic observatories for measuring various components of the magnetic field of the Earth.

b. A sensitive instrument for detecting and measuring changes in the Earth's magnetic field, used in prospecting to detect magnetic anomalies and magnetic gradients in rock formations. See also: airborne magnetometer.


a. A hexagonal mineral, Pb(Fe,Mn) (sub 12) O (sub 19) ; black; ferrimagnetic; at Laangban, Sweden.

b. The mineral group hawthorneite, hibonite, magnetoplumbite, and yimengite.


A form of transmission based on the principle that a magnetic field of force is produced whose strength is varied so as to transmit a torque of corresponding magnitude. With a system of this kind, control of any particular operation is effected through the agency of the magnetorque clutch, while the motor runs continuously at constant speed.


The characteristic of a material that is manifest by strain when it is subjected to a magnetic field; or the inverse. Some iron-nickel alloys expand; pure nickel contracts.

magnetotelluric method

a. An electrical prospecting technique based on an application of telluric currents in which the magnetic fields induced by the alternations in earth currents would be measured simultaneously with the voltage fluctuations between electrodes at the surface. The ratio between the amplitudes of these alternating voltages and the associated magnetic fields would be plotted as a function of frequency.

b. An electromagnetic method of surveying, in which natural electric and magnetic fields are measured. Usually the two horizontal electric-field components plus the three magnetic-field components are recorded; orthogonal pairs yield elements of the tensor impedance of the Earth. This impedance is measured at frequencies within the range 10 (super -5) Hz to 10 Hz.


A monoclinic mineral, (Mg,Fe,Mn) (sub 2) (PO (sub 4) )F ; yellow.


A variety of chromite that contains magnesium. Alternate spelling of magnesiochromite.


An orthorhombic mineral, (Mg,Fe,Mn)(Nb,Ta) (sub 2) O (sub 6) . CF: columbite.


Original form of magnesioferrite.


An isometric and tetragonal mineral, Mn (sub 5) As (sub 3) O (sub 9) (OH,Cl) ; green; forms crusts at Laangban, Sweden, and green to brown selvages at Sterling Hill, NJ.

mahogany ore

Compact mixture of oxides of iron and copper.

mailly stone

A softer sort of limestone, very dusty.

main airway

a. The road along which the principal ventilating current passes.

b. Underground ventilation channel directly connected with a shaft or other entry to a mine.

main-and-tail haulage

A single-track haulage system operated by a haulage engine with two drums, each with a separate rope. The engine is usually located at the out end of the system. The main rope is attached to the out end of the set of tubs, and the tail rope passes around a sheave in, and is then attached to, the rear end of the set. To draw the full set out, the main rope is wound in, the tail rope being allowed to run free. To draw the empty set in, the tail rope is wound in, the main rope being allowed to run free. The tail rope is equal to twice the length of the haulage road. The main-and-tail haulage is adopted when the gradient is irregular and the empty set will not run in by gravity. See also: rope haulage.

main arch

a. The refractory blocks forming the part of a horizontal gas retort comprising the division walls and the roof that covers the retorts and the recuperators.

b. General term for the central part of a furnace roof, particularly used as a syn. for the crown of a glass tank furnace.

main bord gate

York. The heading that is driven slightly to the rise from the shaft.

main bottom

Hard rock below alluvial deposits.

main break

In mine subsidence, the break that occurs over the seam at an angle from the vertical equal to half the dip.

main brow

Eng. See: gate.

main conveyor

See: underground mine conveyor.

main crosscut

The crosscut that traverses the entire mining field and penetrates all deposits. There is such a crosscut at each level, and it is the main one for the level in question. It serves the same purpose as the shaft and thus must have correct cross section, and be particularly well constructed, as repairs to its support would hold up the transport of the entire level.

main drive

A main tunnel driven in the rock underlying a lead and about 50 ft (15.2 m) below the wash dirt. It is used as a drainage tunnel for carrying the water from the drainage holes to the shaft sump and also for the transport of cars from the raises.

main endings

Pairs of narrow coal headings with crosscuts at intervals, driven to form large pillars of coal in panel working. See also: narrow work.

main engine

N. of Eng. The surface pumping engine, usually of the Cornish type.

main entry

a. The principal entry or set of entries driven through the mine from which cross entries, room entries, or rooms are turned.

b. A term used in the United States for the principal horizontal gallery giving access to an underground mine and used for haulage, ventilation, etc. Where two entries are driven in parallel, the term "double entry" is used. With three parallel entries, the term "triple entry" is used. c. An entry driven at right angles with the face slips of the coal. See also: entry. d. A main haulage road. See also: main road.

Maine sampler

A drive-type, split-tube soil-sampling device, usually equipped with a flap or clack valve near the cutting shoe. Usually produced in sizes having outside diameters ranging from 4 to 6-5/8 in (10 to 17 cm).

Maine-type sampler

A soil-sampling device that works essentially on the same principle as a Maine sampler.

main facets

a. The bezel and pavilion facets.

b. Any facet extending from the girdle to the table or from the girdle to the cutlet.

main fans

Main fans produce the general ventilating current of the mine, and are generally of large capacity and permanently installed. They are assisted by natural ventilation, if present, and, if necessary, by booster fans. They are installed to perform a certain duty, and great attention is paid to their efficiency since this governs the cost of performing the duty.

main firing

The firing of a round of shots by means of current supplied by a transformer fed from a main power supply.

main gate

The principal or central heading along which the coal is conveyed from two or more conveyor panels. Normally, the main gate is also the intake airway to the face. See also: double-unit conveyor; bottom gate; mother gate.

main haulage

a. That portion of the haulage system that moves the coal from the secondary haulage system to the shaft or mine opening. The method employed is the same for either longwall or room-and-pillar mining. Any one of four methods may be used: (1) mine cars and battery or trolley locomotives, (2) mine cars and a direct rope haulage, (3) a combination of methods 1 and 2, or (4) belt conveyors.

b. The system by which coal is transported in trains in or out of a slope or drift entry or from the bottom of a shaft.

main haulage conveyor

Generally 500 to 3,000 ft (approx. 150 to 1,000 m) in length. It is used to transport material between the intermediate haulage conveyor and a car-loading point or the outside.

main haulageway

The principal transportation road, drift, tunnel, etc.

main hole

The first or primary borehole from which secondary or branch holes are drilled. Also called original hole; parent hole. CF: branch.

main intake

The trunk or principal intake airway of a mine. The main intake air current is usually split into two or more air currents before reaching the workings.

main levels

The first and leading excavations in mines that are made for the purpose of opening out or winning the material being mined, and that are intended to be the principal roadways of the mine.

main-line locomotive

A large, high-powered locomotive that hauls trains of cars over the main haulage system.

main-line motorman

In bituminous coal mining, a person who operates a mine locomotive to haul cars over the main haulage tracks underground or at the surface, as distinguished from the branch lines.

main return

represents the total quantity of air; i.e., after the air splits have reunited.

main road

The principal underground road in a district along which mined material is conveyed to the shafts, generally forming the main intake air course of each district. See also: main entry.

main rod

Corn. See: pump rod.

main roof

The rock above the immediate roof.

main rope

The rope that pulls a train of loaded cars out along a haulage plane, as opposed to a tail rope that pulls a train of empty cars in, as in main-and-tail haulage. See also: pull rope.

main-rope haulage system

This system of haulage is used for hauling loaded trains of tubs or cars up, or lowering them down, a comparatively steep gradient that is not steep enough, in the latter case, for a self-acting incline. In the normal system, a single track only is required. The electrically driven or compressed-air-driven engine has a single drum that runs loose on the forged-steel drum shaft; it is controlled by the brake when lowering the empty train, and is clutched to the shaft by means of a dog clutch when hauling the loaded train up the gradient.

main-rope rider

In bituminous coal mining, one who has charge of and rides trips (trains) of cars hauled in and out of the mine along the main cable haulageway.

main-rope system

A system of underground haulage in which the weight of the empty cars is sufficient to draw the rope in.

main separation door

A wooden or steel door erected near the pit bottom to prevent the intake air leaking into the main return airway or upcast shaft; a door to direct the main intake air in toward the workings. It may be fitted with an appliance, or shutter, to ease the opening for traveling purposes. See also: fan drift doors.

mains firing

Firing blasts from a mains supply.

main shaft

The line of shafting that receives its power directly from the engine or motor and transmits power to other parts.

mains lighting

A system of underground mine lighting in which the lamps are fed from the main electrical supply. It is used principally at the pit bottom, using filament lamps in either transparent well glass or prismatic bulkhead fittings.

main-slope engineer

In bituminous coal mining, one who operates the hoisting engine for raising or lowering workers, material, coal, and rock along the main haulage slope (incline) of a mine having one or more auxiliary or relay slopes.

maintaining levels

In quarrying, consists of the removal by blasting of rock protruding above the level of the quarry floor or bench, to allow the movement of loading and transport equipment.


Fr. The face of workings in inclined or vertical seams consisting of a series of steps each about 6 ft (1.8 m) high, and forming the working place for one person.


Proper care, repair, and keeping in good order.

main tie

Tension member connecting the feet of a roof truss, usually at the level of bearing on the wall plate or padstone.

main transport

The conveying or haulage of mined material from the mining area subsidiary transport to the shaft bottom or surface. For the main transport of coal, the trend is toward trunk conveyors or locomotive haulage. See also: subsidiary transport; underground haulage.

main way

A gangway or principal passage.


See: thorogummite.

Majac mill

A mill for dry-grinding mica by means of fluid energy. It consists of a chamber containing two horizontal directly opposed jets. Mica is fed continuously from a screw conveyor into this chamber. The particle size of the product from this mill can be controlled over a broad range down to the micrometer sizes.

major diameter

Formerly called outside diameter. It refers to the largest diameter of a thread on a screw or nut.

major face

Used in widely different meanings in different manufacturing plants; the meaning of the term depends on the special process of cutting used. Thus, the faces of the major rhombohedron r 1011 are spoken of as the major face when BT wafers are cut directly from a faced mother crystal. Also applied to the prism faces that terminate in the faces of the major rhombohedron, etc.

major mine disaster

Defined by the Mine Safety and Health Administration, U.S. Department of Labor, as any accident that results in the death of five or more persons.

major principal plane

The plane normal to the direction of the major principal stress.

major principal stress

The largest (with regard to sign) principal stress.


A wide portion of a lode. CF: pinch.

make gas

Mid. To yield or produce gas. A seam of coal that gives off combustible gas is said to make gas.

make of water

The rate of entry of water into a mine or part of a mine. Also called growth.


To assemble; to couple or screw together. Usually applied to the process of assembling the component parts of a drill string or pipe system.

makeup bunker

See: makeup shed.

makeup medium

Medium or medium solids added to the circuit to replace losses during the separating operation.

makeup shed

A surface building at which explosives, drawn from the magazine, are issued and where the charges are prepared or made up. Syn: makeup bunker.

makeup time

The time required to couple together the component parts of a drill or casing string and the lowering of such a string to the working position in a borehole.

makeup water

a. Water supplied to a washery to replace that lost from the circuit.

b. Water supplied to replenish that lost by leaks, evaporation, etc.

making hole

a. The depth gained in the day's drilling.

b. The act of, or portion of work time spent in, actual drilling and advancement of a bore or drill hole.


Newc. The small coal hewn out in undercutting or channeling. Also, in some localities, called bug dust.


A monoclinic mineral, Cu (sub 2) CO (sub 3) (OH) (sub 2) ; dimorphous with georgeite; bright green; occurs with azurite in oxidized zones of copper deposits; a source of copper. Syn: Atlas ore.


a. A pale-colored, translucent variety of diopside with good (001) parting; also diopside from Sala, Sweden.

b. See: diopside.


A metamict variety of zircon. Also spelled malakon, malacone.


An isometric mineral, Au (sub 2) Bi ; pink to silver-white; intermetallic compound. Syn: black gold.

male thread

See: pin thread.

maletra furnace

A hand reverberatory furnace for roasting finely divided ore entirely without the aid of extraneous heat.


A mafic nepheline syenite. Fifty percent of the rock is composed of aegirine-augite; the remainder is nepheline and orthoclase in about equal amounts. Accessories include apatite, biotite, titanite, and opaque oxides.


An aluminous variety of halloysite.


A variety of tetrahedrite that contains lead and silver.


Eng. A heavy hammer. A drawing or prop mall is a long-handled mall used when withdrawing timber.


A trigonal mineral, Na (sub 2) SiF (sub 6) . (Not mallardite.)


Soft turf containing lumps of ore, Derbyshire, U.K.


A monoclinic mineral, MnSO (sub 4) .7H (sub 2) O ; melanterite group. (Not malladrite.)


a. The characteristic of metals that permits plastic deformation in compression without rupture. See also: plastic deformation.

b. Minerals are malleable when slices cut from them may be flattened out under a hammer. Examples are native gold; silver; copper; platinum.


a. Said of a mineral, e.g., gold, silver, copper, platinum, that can be plastically deformed under compressive stress, e.g., hammering.

b. A mineral that can be sliced and the slices hammered flat without breaking, e.g., gold, copper. CF: sectile; flexible.

malleable cast iron

A cast iron made by a prolonged anneal of white cast iron in which decarburization or graphitization, or both, take place to eliminate some or all of the cementite. The graphite is in the form of temper carbon. If decarburization is the predominant reaction, the product will have a light fracture, (whiteheart malleable); otherwise, the fracture will be dark (blackheart malleable). Pearlitic malleable is a blackheart variety having a pearlitic matrix along with, perhaps, some free ferrite. See also: iron.

malleable mineral

A mineral that may be flattened or deformed by hammering without breaking, for example, native copper or gold.

malleable nickel

Nickel obtained by remelting and deoxidizing electrolytic nickel and casting it into ingot molds. It can be rolled into sheet and used in equipment for handling food, and for coinage, condensers, and other purposes where resistance to corrosion, particularly by organic acids, is required.


Annealing white cast iron in such a way that some or all of the combined carbon is transformed to graphite or, in some instances, part of the carbon is removed completely.


To shape into a plate or leaf by beating or hammering; said of metal.


a. A hard, cherty, grayish-white sandstone, specif. the Malmstone from the upper part of the Upper Greensand (Cretaceous) of Surrey and Sussex in England, used as a building and paving material.

b. A marly or chalky rock.


A term used in the Southwestern United States and Mexico for a region of rough and barren lava flows. The connotation of the term varies according to the locality. Etymol: Spanish, mal pais, bad land.


A variety of andalusite, resembling chiastolite, showing in cross section a maltese cross of pure material separated by areas of impure material.


a. Various natural tars resulting from the oxidation and drying of petroleum. See also: mineral tar; pittasphalt.

b. A black viscid substance intermediate between petroleum and asphalt. Also called malthite. c. A variety of ozocerite.


A scaly, sometimes massive, white or yellowish clay related to fuller's earth, having a Si-Al ratio of about 4.


Of, or pertaining to, smoothly rounded masses resembling breasts or portions of spheres; descriptive of the shape of some mineral aggregates, such as malachite or limonite; similar to but a larger size than botryoidal.

mammillary structure

See: pillow structure.


Said of a mineral displaying large spheroidal surfaces, e.g., malachite.

managerial organization

Coordination of functional units and presentation of the results of their achievements in policy-guiding form as facts, conclusions, and recommendations. Efficient integration of the operations managed.


An orthorhombic mineral, Li (sub 2) Al (sub 4) (Si (sub 2) AlB)O (sub 10) (OH) (sub 8) ; kaolinite-serpentine group.


a. A hexagonal mineral, Mg (sub 6) Al (sub 2) (CO (sub 3) )(OH) (sub 16) .4H (sub 2) O ; dimorphous with hydrotalcite.

b. The mineral group barbertonite, chlormagaluminite, manasseite, and sjoegrenite.


a. Spotted ore, Spain.

b. A commercial grade of mica which is stained to very slightly spotted, Brazil.

Manchurian jade

See: soapstone.


See: amygdaloid.


a. A miner's pick.

b. A usually tapered or cylindrical axle spindle, or arbor that is inserted into a hole in a piece of work so as to support the work during machining. c. A metal bar that serves as a core around which metal or other material may be cast, molded, forged, bent, or otherwise shaped. d. Any of a train of jointed units intended to be pulled through an underground duct as each joint is made to ensure perfect alinement, or through a steel pipe in process of welding to ensure a smooth interior. e. The shaft and bearings on which a tool (as a grinding disk or circular saw) is mounted. f. A temporary interior support for a thin-walled tube (as a tubular steel pile to be filled later with concrete) being driven into something.


A miner's pick.

Manebach law

A type of twinning in the monoclinic crystal system. The basal pinacoid is the twinning plane.

Manebach twin

A monoclinic crystal twinned across the basal pinacoid, according to the Manebach law, e.g., orthoclase.

man engine

See: man machine.


A variety of andalusite containing 6.91% Mn (sub 2) O (sub 3) . It differs from ordinary andalusite in its grass-green color and strong pleochroism. From Vestana, Sweden.


An isometric mineral, (Ca,Na) (sub 3) (Mn,Mg) (sub 2) (AsO (sub 4) ) (sub 3) ; forms a series with berzeliite and is yellow to orange.


See: alabandite.


Variety of andalusite containing manganese. Alternate spelling of manganandalusite.


See: piemontite.


A gray-white, hard, brittle metallic element. Symbol, Mn. Manganese does not occur uncombined in nature, but its minerals are widely distributed. Pyrolusite (MnO (sub 2) ) and rhodochrosite (MnCO (sub 3) ) are the most common minerals. The discovery of large quantities of manganese nodules on the ocean floor, containing about 24% manganese, holds promise as a source of manganese. Used to form many important alloys, esp. with steel, aluminum, and antimony; used in dry cells and glass, and in the preparation of oxygen, chlorine, and medicines.

manganese-aluminum garnet

See: spessartine.

manganese bronze

Alloy of 59% copper, 1% tin, and up to 40% manganese. Practically a brass with high tensile strength and toughness. Used for ship's impellers and such fittings as must withstand corrosion by seawater.

manganese garnet

See: spessartite.

manganese glance

See: alabandite.


A monoclinic mineral, (Mn,Mg) (sub 3) (AsO (sub 4) ) (sub 2) .8H (sub 2) O; vivianite group.

manganese hydrate

See: wad.

manganese minerals

Those in commercial production are pyrolusite, psilomelane, braunite, and manganite. Manganese is used chiefly in steel manufacture.

manganese nodules

The concretions, primarily of manganese salts, covering extensive areas of the ocean floor. These vary in size from extremely small to some 6 in (15.2 cm) in diameter. They have a layer configuration and may prove a useful source of minerals.

manganese ore

A term used for ore containing 35% or more manganese; it may include concentrate, nodules, or synthetic ore.

manganese oxide

There are several manganese oxides, the commonest being MnO (sub 2) (pyrolusite). It is used as a coloring oxide (red or purple); mixed with the oxides of cobalt, chromium, and iron, it produces a black. This oxide is also used to color facing bricks, and to promote adherence of ground-coat vitreous enamels to the base metal. See also: manganite; psilomelane.

manganese sicklerite

See: sicklerite.

manganese silicate

See: rhodonite.

manganese spar

See: rhodonite; rhodochrosite.

manganiferous iron ore

A term used for iron ores containing 5% to 10% manganese.

manganiferous ore

A term used for any ore of importance for its manganese content containing less than 35% manganese but not less than 5%. See also: natural ore.


A monoclinic mineral, MnO(OH) ; trimorphous with feiknechtite and groutite; a hydrothermal vein mineral; an ore of manganese. Syn: gray manganese ore; sphenomanganite.


A monoclinic mineral, KNa (sub 2) Li(MN,Fe) (sub 2) Ti (sub 2) Si (sub 8) O (sub 24) ; forms a series with neptunite. See also: neptunite.


A variety of calcite that contains manganese carbonate and is closely related to rhodochrosite. Syn: kutnohorite.


An isometric mineral, K (sub 2) Mn (sub 2) (SO (sub 4) ) (sub 3) ; rose-red; forms tetrahedra in cavities in recent lavas on Mt. Vesuvius, Italy.


a. See: rhodonite.

b. A general term for rocks composed of manganese minerals, esp. manganese oxides such as wad and psilomelane.


A manganoan variety of biotite.


An intermediate member of the rhodochrosite-siderite series.


An isometric mineral, MnO ; periclase group; emerald-green; forms octahedra that blacken on exposure to air.


An orthorhombic mineral, MnTa (sub 2) O (sub 6) ; dimorphous with manganotapiolite; forms series with manganocolumbite and with ferrotantalite.


A hexagonal mineral, (Mn,Fe) (sub 8) Si (sub 6) O (sub 15) (OH,Cl) (sub 10) ; dimorphous with brokenhillite; forms a series with ferropyrosmalite.

mangrove coast

A tropical or subtropical low-energy coast with a shore zone overgrown by mangrove vegetation. Such coasts are common in Indonesia, Papua New Guinea, and other tropical regions. The marine coast of southern Florida is the only significant U.S. example.


a. A safety hole.

b. Cubicles cut into the solid strata or built into the gob pile along haulageways in which miners can be safe from passing locomotives and cars. Also called refuge hole. c. A refuge hole constructed in the side of a gangway, tunnel, or slope. d. A small and generally very short passage used only for the ingress and egress of the miners. e. A hole in cylindrical boilers through which a worker can get into the boiler to examine and repair it. f. A small passage connecting a level with a stope, or with the level next above.

manhole cover

A movable cast-iron plate fitting a cast-iron frame bedded on a rebated concrete slab or kerb over a manhole. Covers over foul drains are formed to prevent escape of foul air.

manila rope

Broadly, rope or cordage formed from twisted fibers obtained from abaca, agave, or hemp plants.

manipulated variable

In mineral processing, a quantity or condition that is varied as a function of the actuating signal so as to change the value of the controlled variable.


a. A machine for moving and turning over hot billets or blooms of iron or steel in the process of rolling.

b. A mechanical device used for safe handling of radioactive materials. Frequently, it is remotely controlled from behind a protective shield.

manless coal face

A coal face mined by remotely controlled equipment that eliminates the need for workers in dangerous places.

manless coal mining

Longwall coal faces equipped for the automatic starting, stopping, and steering of power-loading machines as well as the manipulation of electric trailing cables, including air and water hoses; controlled automatic advancing of face conveyors as well as advancing and setting of roof supports. Each and all operations are correctly phased and accomplished from a remote point. With the advent of electronics and automation techniques, the prospects of manless coal mining are very promising.

manless face

A longwall face on which the coal is cut and brought out to the gate road mechanically, without the aid of miners on the face. The face is unsupported. In general, the coal seam is thin but of high grade, and some type of rapid plow is employed. See also: coal-sensing probe; ram scraper.


An air lock through which workers pass to a working chamber that is under air pressure.

man machine

Corn.; Derb. An obsolete term for a mechanical lift for lowering and raising miners in a shaft by means of a reciprocating vertical rod of heavy timber with platforms at intervals, or of two such rods moving in opposite directions. In the former case, stationary platforms are placed in the shaft, so that the miner in descending, for instance, can step from the moving platform at the end of the downstroke and step back upon the next platform below at the beginning of the next downstroke. When two rods are employed, the miner steps from the platform on one rod to that on the other. Syn: man engine; movable ladder.

manmade diamond

Diamond produced synthetically. Also called MM diamond. See also: diamond; synthetic diamond.

Mannheim process

Contact method of catalyzing SO (sub 2) to SO (sub 3) in two stages, using first iron oxide and second platinized asbestos as catalysts.

Manning's formula

An empirical formula for the value of the coefficient, C, in the Chezy formula, the factors of which are the hydraulic radius and a coefficient of roughness; a simplification of the Kutter formula.


Staff. A small pillar of coal left in a critical spot; also, a principal support in thick coal workings.


a. Any instrument that measures gaseous pressure.

b. Measures pressure or a pressure difference by balancing the applied pressure against the hydrostatic head of a column of liquid of known density. In practice, most manometers measure a pressure difference, so that if an absolute pressure is to be measured, it is essential to have access to an accurate barometer to determine the atmospheric pressure. c. An instrument designed to give a continuous record of the pressure of an explosion at the point where the instrument is located. See also: micromanometer; piezometer; two-liquid differential manometer; U-tube manometer; vernier-reading manometer; water gage.

manometer calibration

Many manometers require calibration, and this may be carried out by the (1) static method in which simultaneous readings of the manometer under test and the primary standard are taken when one limb of the manometer and the standard are connected to a variable pressure source, the other limbs being connected to a source of constant pressure, or (2) the dynamic method in which the difference in pressure obtained between a low-speed atmospheric wind-tunnel hole (static pressure) and the atmospheric static pressure is used to carry out the calibration. One limb of the manometer and the low-pressure side of the Chattock-Fry are connected to the tunnel-wall hole (reference variable pressure), while the other limb of the manometer is connected to the atmospheric outlet of the Chattock-Fry.

manometric efficiency

a. The ratio of the actual head developed to the velocity pressure of air moving at the fan-tip speed, equal to one-half the theoretical head of a radial-tip fan.

b. An indication of the capability of the fan to produce pressure. It is the ratio of the initial depression to the theoretical depression. Manometric efficiency = 4,380 total water gage / U (super 2) , where U = tip speed in feet per second of fan blades. c. The chief value of the manometric efficiency lies in its being a rough check on the mechanical efficiency of the fan. See also: theoretical depression.


See: manometer.


The science of determining the density of gases and vapors.

man-riding car

A car or carriage designed for the riding of miners to and from the workings. The car body has a low center of gravity to avoid the risk of overturning and is fitted with track brakes and an overspeed clutch. The train set is arranged to brake from the rear to avoid pileup, and the brakes are applied immediately on overspeed from a preset velocity.

man-riding conductor

A worker appointed by the mine manager to be in charge of the running of a train of man-riding cars. This worker is the responsible person for starting and stopping the vehicles, for giving the proper signals, and for seeing that the safe seating capacity is not exceeded. During the shift this worker is employed on other duties.


An orthorhombic mineral, AlAsO (sub 4) .2H (sub 2) O ; variscite group; forms a series with scorodite.


The output or work done by a worker in one shift; a basis for assessing the magnitude of a job to complete.

Man-Ten steel alloy

An alloy containing 0.35% carbon as maximum, from 0.25% to 1.75% manganese, 0.10% to 0.30% silicon, 0.01% to 0.25% copper, 0% to 0.40% molybdenum, and 0% to 0.20% vanadium. Used for bodies and doors of stripping shovel dippers, which have manganese steel for bail, lip, and renewable teeth.


a. The soil or other unconsolidated rock material commonly referred to as overburden. See: surface. See also: burden; cover.

b. A sheath of manganese steel that fits over the iron or steel cone of the breaking (gyrating) head of a gyratory crusher. c. That part of a blast furnace that carries the weight of the stack, continuing up from the bosh. d. See: mantle rock; regolith. e. The outer zone in a zoned crystal; an overgrowth. f. The zone of the Earth below the crust and above the core, which is divided into the upper mantle and the lower mantle, with a transition zone between.

mantle rock

See: regolith.


A flat-lying, bedded deposit; either a sedimentary bed or a replacement strata-bound orebody. Etymol: Spanish, vein, stratum. CF: bed vein.

manual haulage

The practice of pushing tubs, trams, etc., by hand. See also: hand tramming.

manual takeup

A hand-operated mechanism for adjusting the takeup or movable pulley.

manual-type belt-tensioning device

A hand-operated mechanism for adjusting a takeup pulley to vary the tension in a conveyor belt. The most common types are chain-jack, sylvester, rack, and screw.

manual winding control

A system in which the winder is controlled in the conventional manner by the driver, following the usual bell signals from the onsetter and the banksman. The system of control ensures that the speed of the winder follows closely the position of the driver's level, driving or dynamic braking being applied automatically to the motor as needed to preserve the chosen speed. See also: automatic cyclic winding.

manufactured gas

A mixture of gaseous hydrocarbons produced from coal or oil. See also: gas.

manufactured marble

a. A mixture of marble dust and plastics.

b. A mixture of powdered stone and plastics.

manufactured sand

Fine aggregate produced by crushing rock.


a. A compartment, vertical or inclined, for the accommodation of ladders, pipes, and timber chutes. The drivage may be a winze or a raise and its purpose is to give convenient access to a stope. Also called ladderway.

b. A passageway for the use of miners only; an airshaft; a chute. c. Eng. See: manhole. d. A passage in or into a mine used as a footpath for workers. e. A short heading between two chutes.