Appendix:Dictionary of Mining, Mineral, and Related Terms/M/4

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A monoclinic mineral, AgSbS (sub 2) ; soft; metallic; in low-temperature hydrothermal veins; an ore of silver.


A granite having miarolitic cavities; a textural modification of normal granite.


A chorismite having miarolitic cavities or remnants thereof; a variety of ophthalmite.


A term applied to small irregular cavities in igneous rocks, esp. granites, into which small crystals of the rock-forming minerals protrude; characteristic of, pertaining to, or occurring in such cavities. Also, said of a rock containing such cavities. CF: drusy.

miarolitic cavity

A cavity of irregular shape in certain plutonic rocks. Crystals of the rock constituents sometimes project into the cavity. CF: druse; vug.


A mixture of strontianite and calcite.


a. A group of phyllosilicate minerals having the general composition, X (sub 2) Y (sub 4-6) Z (sub 8) O (sub 20) (OH,F) where X=(Ba,Ca,Cs,H (sub 3) O,K,Na,NH (sub 4) ), Y=(Al,Cr,Fe,Li,Mg,Mn,V,Zn), and Z=(Al,Be,Fe,Si); may be monoclinic, pseudohexagonal or pseudo-orthorhombic; soft; perfect basal (micaceous) cleavage yielding tough, elastic flakes and sheets; colorless, white, yellow, green, brown, or black; excellent electrical and thermal insulators (isinglass); common rock-forming minerals in igneous, metamorphic, and sedimentary rocks. See also: brittle mica. Syn: glimmer; isinglass.

b. The mineral group anandite, annite, biotite, bityite, celadonite, chernykhite, clintonite, ephesite, ferri-annite, glauconite, hendricksite, kinoshitalite, lepidolite, margarite, masutomilite, montdorite, muscovite, nanpingite, norrishite, paragonite, phlogopite, polylithionite, preiswerkite, roscoelite, siderophyllite, sodium phlogopite, taeniolite, tobelite, wonesite, and zinnwaldite.


a. Consisting of or containing mica; e.g., a micaceous sediment.

b. Resembling mica; i.e., thinly foliated.

micaceous iron ore

Hematite in which the texture is foliated or micaceous; some micaceous varieties are soft and unctuous.

micaceous sandstone

A sandstone containing conspicuous layers or flakes of mica, usually muscovite. Syn: metaxite.

mica house

A shop where hand-cobbed mica is rifted, trimmed, graded, and qualified. Syn: trimming shed.


Trade name for a form of built-up mica used for insulating.

mica peridotite

A peridotite consisting principally of altered olivine and biotite.

mica plate

An accessory introduced into the optic path of a polarized-light microscope to produce a first-order gray interference color. Syn: glimmer plate; lambda plate. See also: accessory plate.

mica powder

A dynamite in which the dope consists of fine scales of mica.

mica schist

A schist whose essential constituents are mica and quartz, and whose schistosity is mainly due to the parallel arrangement of mica flakes.


An isometric mineral, (Pd,Pt)BiTe ; pyrite group; metallic; at Sudbury, ON, Canada and Monchegorsk, Kola Peninsula, Russia.

Michigan cut

a. In the United States, a cut that consists of drilling a hole with a large diameter or a number of holes of smaller diameter at the center of the heading and parallel to the direction of the tunnel. These holes are not charged. The remaining bench holes are then broken out towards these holes.

b. See: burned cut.

Michigan slip

A very plastic, tough, fine-grained impure clay, similar to Albany slip clay; used as a bonding and plasticizing agent in grinding wheels, refractories, etc., and as a suspension agent for glassy frit in vitreous enamels.


a. A maceral of the inertinite group consisting of granular material without cellular structure; one of the principal components of durain and clarain.

b. Proposed by the Heerlen Congress, 1935, as a substitute for micronite.


A coal constituent similar to material derived from finely macerated vegetation.


a. A descriptive term originally used for the semiopaque crystalline matrix of limestones, consisting of chemically precipitated carbonate mud with crystals less than 4 mu m in diameter, and interpreted as a lithified ooze. The term is now commonly used in a descriptive sense without genetic implication.

b. A limestone consisting dominantly of micrite matrix; e.g., lithographic limestone.


a. A prefix that divides a basic unit by 1 million or multiplies it by 10 (super -6) . Abbrev., mu .

b. A prefix meaning small. When modifying a rock name, it signifies fine-grained hypabyssal, as in microgranite. CF: macro-.


One-millionth of an ampere; 10 (super -6) A; abbrev., mu a.


See: cryptocrystalline.


One of the tiny hollow spheres of glass or plastic that are added to explosive materials to enhance sensitivity and control density by assuring an adequate content of entrapped air.


A unit of pressure commonly used in acoustics. One microbar is equal to 1 dyn/cm (super 2) .


a. A poorly sorted sandstone containing large angular particles of sand set in a fine silty or clayey matrix; e.g., a graywacke. It is somewhat less micaceous than a siltstone.

b. A breccia within fragments of a coarser breccia. c. A well-indurated, massive rock that has been crushed to very fine grain size through cataclastic flow, commonly in detachment faults.


Applied to chemical reactions conducted on the stage of a microscope and viewed through the microscope.


a. Applied to a clastic or fragmental rock composed of very small particles.

b. Said of coal that is composed mainly of fine particles; e.g., cannel coal.


A triclinic mineral, KAlSi (sub 3) O (sub 8) ; feldspar group; pseudomonoclinic; dimorphous with orthoclase; a major rock-forming mineral in granites, pegmatites, and metamorphic rocks; may be a detrital mineral in arkoses and graywackes. CF: orthoclase.


A sedimentary rock composed of relatively coarse sand grains in a very fine silt or clay matrix.

microcosmic salt

See: stercorite.


See: cryptocrystalline.


Said of the texture of a rock consisting of or having crystals that are small enough to be visible only under the microscope; also, said of a rock with such a texture. Syn: cryptocrystalline; micromeritic.


See: trace element.


Those characteristic and distinctive aspects of a sedimentary rock that are visible and identifiable only under the microscope (low-power magnification).


A unit of capacitance; one-millionth of a farad; symbol, mu F.


See: cryptocrystalline.


Having a microscopic flow texture.


a. The study of the microscopic features of rocks.

b. The study of the relationships of microorganisms to geologic and geochemical processes.


Having a microscopic granitoid structure.


a. Said of the texture of a microcrystalline, xenomorphic igneous rock. Also, said of a rock with such a texture.

b. Minutely granular; specif. said of the texture of a carbonate sedimentary rock wherein the particles are mostly 10 to 60 mu m in diameter and are well-sorted, and the finer clay-sized matrix is absent. Also said of a sedimentary rock with such a texture.


A graphic reproduction of a magnified object as seen through a microscope. When it is a photograph, it is called a photomicrograph.


Said of the graphic texture of an igneous rock that is distinguishable only with the aid of a microscope; also, said of a rock having such texture.


The hardness of microscopic areas or of the individual microconstituents in a metal, as measured by means such as the Tukon, Knoop, or scratch methods.


One microhm equals 10 (super -6) Omega , which equals 10 (super 3) electromagnetic units. Symbol, mu Omega .


Microite is found in many coals and occurs in large quantities in Gondwana coals and in Permocarboniferous coals of the former U.S.S.R. It is most abundant in coals with little exinite, or coals of high rank in which exinite cannot be recognized, and may occur in very persistent thick bands. It is present in small amounts in Carboniferous coals of the Northern Hemisphere.


A well log obtained with an arrangement of electrodes similar to a miniature laterolog but disposed in concentric fashion in an insulating pad. The current from a central electrode is focused and flows out in a pattern that resembles the shape of a trumpet. As in the microlog, the electrodes are mounted on a pad that is held against the wall of the hole by springs. The microlaterolog serves a purpose similar to that of a microlog, investigating only a small volume of rock immediately adjacent to the hole. Syn: trumpet log.


a. A microscopic crystal that polarizes light and has some determinable optical properties. CF: crystallite; crystalloid. Syn: microlith.

b. A pale-yellow, reddish, brown, or black isometric mineral of the pyrochlore group: (Ca,Na) (sub 2) Ta (sub 2) O (sub 6) (O,OH,F). It is isomorphous with pyrochlore, and it often contains small amounts of other elements (including uranium and titanium). Microlite occurs in granitic pegmatites and in pegmatites related to alkalic igneous rocks, and it constitutes an ore of tantalum. Syn: djalmaite.


See: microlite.


A typical association of macerals in coals, occurring in bands at least 50 mu m wide. Microlithotype names bear the suffix "-ite". See also: lithotype.


Said of the texture of a porphyritic igneous rock in which the groundmass is composed of an aggregate of differently oriented or parallel microlites in a glassy or cryptocrystalline mesostasis.


Essentially a U-type gage employing a micrometer to measure the change in inclination of the gage from its zero or datum position. Normally, micromanometers are used in the laboratory for such purposes as the calibration of secondary manometers and, in conjunction with pressure measurement, in low-speed atmospheric wind tunnels. See also: manometer.


An obsolete syn. of microcrystalline. See also: microcrystalline.


a. An instrument for measuring very small dimensions or angles. Used in connection with a microscope or a telescope. There are a great variety of forms, but in nearly all, the measurement is made by turning a very fine screw, which gives motion to a scale, a spider line, a lens, a prism, or a ruled glass plate.

b. A unit of length, equal to one-millionth of a meter. Symbol, mu m. (1 mu m = 10 (super -6) m). Formerly called micron. c. A micrometer caliper.

micrometer caliper

A caliper with a graduated screw attachment for measuring minute distances.

micrometer-reading manometer

See: vernier-reading manometer.


The study of very fine particles.


One-millionth of a millimeter; abbrev., mmu .


Former term for micrometer.

micronized mica

An ultrafine material produced in a disintegrator that has no moving parts but depends on jets of high-pressure superheated steam to reduce the mica to micrometer sizes. Micronized mica is produced in particle size ranges of 10 to 20 mu m and 5 to 10 mu m.


A special type of dry-grinding machine in which micronized mica is produced. It consists of a disintegrator that has no moving parts but depends on jets of high-pressure superheated steam for reducing the mica to micrometer sizes.

micronizer mill

Disintegrator, in which feed particles are entrained in a pressure jet (steam or air) and whirled through a cylindrical chamber with sufficient force to break them.


A less-preferred syn. of granophyre. See also: granophyre.


Exsolution lamellae in alkali feldspar visible only with the aid of a microscope. See also: cryptoperthite; perthite.

micropetrological unit

See: maceral.


See: photomicrograph.


Porosity visible only with the aid of a microscope.


An instrument used to produce enlarged images; it consists of a lens (or lenses) of the objective and an ocular set into a tube, with or without other accessories, and held by an adjustable arm over an object stage.


a. Of, relating to, or conducted with a microscope or microscopy.

b. So small or fine as to be invisible or not clearly distinguishable without the use of a microscope. CF: macroscopic; megascopic.


The art and practice of using a microscope for identification and analysis of objects. See also: ore microscopy; reflected-light microscope.


One-millionth of a second; abbrev.: mu sec, mu s.


a. Any thin section used in microscopic analysis.

b. A polished section.


earthquake and that have a period of 1.0 to 9.0 s. They are caused by a variety of natural and artificial agents, esp. atmospheric events. Syn: seismic noise.

microseismic instrument

An instrument for observing the behavior of roof strata and supports. The device is inserted in 4-ft (1.2-m) long 1-1/2-in (3.8-cm) diameter holes, drilled at selected points, for listening to subaudible vibrations which are known to precede rock failure.

microseismic movement

See: microseism.

microseismic rate

The number of microseisms per unit of time.

microseismic region

Area in which an earthquake is registered by instruments only.


An apparatus for indicating the direction, duration, and intensity of microseisms. Also called microseismograph.


Calcite matrix in limestones, occurring as uniformly sized and generally loaf-shaped crystals ranging from 5 mu m to more than 20 mu m in diameter.


Said of the spherulitic texture of an igneous rock that is distinguishable only with the aid of a microscope, owing to the small size of the spherules. Also, said of a rock having such texture.


Microscopic scratch developed on the polished surface of a rock or mineral as a result of abrasion.


a. Structural features of rocks that can be discerned only with the aid of the microscope.

b. The structure of polished and etched metals as revealed by a microscope at a magnification greater than 10 diameters.


A type of grain boundary indicating differential solution between two minerals and characterized by fine interpenetrating teeth; often marked by a little opaque material. See also: stylolite.


The thin vitrainlike bands present in clarain, having a maximum thickness of about 1/10 in (2.5 mm) with a tolerance of 1 mm, and a minimum thickness of 0.05 mm (50 mu m).


One-millionth of a volt; 10 (super -6) V; symbol, mu V.


One-millionth of a watt; symbol, mu W.


See: foyaite; nepheline syenite.

Mid-Atlantic Ridge

A mountain range that extends parallel to the continental margins in mid-ocean in both the North and South Atlantic Oceans. It rises 6,000 ft above the ocean floor and surfaces as the Azores, Ascension Island, Saint Helena, and Tristan da Cunha islands.


Pertaining to a segment of geologic time intermediate between Late and Early, or to rocks intermediate between Upper and Lower. Thus, rocks of the Middle Jurassic Series were formed during the Middle Jurassic Epoch. CF: Upper; Lower.

middle cut

A machine cut in the midsection of a coal seam; sometimes adopted in thick seams (over 4 ft or 1.2 m) with a layer of dirt or inferior coal in the middle. A middle cut would be made with a turret coal cutter. See also: bottom cut; top cut. Syn: intermediate cut.

middle man

A stratum of rock dividing or separating two seams or beds of coal.

middle prop

See: center prop.


See: middlings.


A brown, resinous, brittle mineral found between layers of coal at the Middleton collieries, near Leeds, England, and also at Newcastle.


a. That part of the product of a washery, concentration, or preparation plant that is neither clean mineral product nor reject (tailings). It consists of fragments of coal ore mineral and gangue. The material is often sent back for crushing and/or retreatment. Syn: middles.

b. In two-component ore, particles incompletely liberated by comminution into concentrate or gangue. In complex ores, in addition to incomplete liberation, there may be multiphased particles of middling or intermediate species that react too feebly to treatment to report as concentrate or tailing.

middlings elevator

An elevator that removes material for further treatment or for disposal as an inferior product.


Scot. The middle one of three landing places in a shaft.


In mining, a support to the center of a tunnel.


N. of Eng. Lamp (not safety) carried by trammers, etc.

midge stone

Moss agate with inclusions resembling a swarm of mosquitoes. Also called gnat stone; mosquito agate.

midget impinger

A dust-sampling apparatus almost identical in principle and design with the regular Greenburg-Smith impinger, the main difference being its smaller size and the fact that only a 12-in (30.5-cm) head of water is required for its operation. See also: Greenburg-Smith impinger.

mid-ocean ridge

A continuous, seismic, median mountain range extending through the North and South Atlantic Oceans, the Indian Ocean, and the South Pacific Ocean. It is a broad, fractured swell with a central rift valley and usually extremely rugged topography; it is 1 to 3 km in elevation, about 1,500 km in width, and over 84,000 km in length. According to the hypothesis of sea-floor spreading, the mid-ocean ridge is the source of new crustal material. See also: rift valley. Syn: mid-ocean rise; oceanic ridge.

midocean rift

See: rift valley.

mid-ocean rise

See: mid-ocean ridge.


a. Scot. Mine workings above or below in the same mine or colliery.

b. See: middoor.


A variety of dolomite from Miemo, Tuscany, Italy.


An isometric mineral, (Ag,Cu)I ; canary yellow.


A brown variety of pyromorphite containing calcium from Mies, Czech Republic.


Mobile, or potentially mobile, mixture of solid rock material(s) and magma, the magma having been injected into or melted out of the rock material. Etymol: Greek, mixture.


A composite rock composed of igneous or igneous-appearing and/or metamorphic materials that are generally distinguishable megascopically. See also: composite gneiss. CF: chorismite; injection gneiss.


Formation of a migmatite. The more mobile, typically light-colored, part of a migmatite may be formed as the result of anatexis, lateral secretion, metasomatism, or injection.


a. The movement of oil, gas, or water through porous and permeable rock. Parallel (longitudinal) migration is movement parallel to the bedding plane. Transverse migration is movement across the bedding plane.

b. The process by which events on a reflection seismogram are mapped in an approximation of their true spatial positions. It requires knowledge of the velocity distribution along the raypath. Also, the seismic correction that is applied. c. The movement of a topographic feature from one locality to another by the operation of natural forces; specif. the movement of a dune by the continual transfer of sand from its windward to its leeward side. d. The slow downstream movement of a system of meanders, accompanied by enlargement of the curves and widening of the meander belt. e. A broad term applied to the movements of plants and animals from one place to another over long periods of time.

migration of oil

The movement or seepage of oil through rocks wherever they are sufficiently permeable to allow such passage; of considerable importance in oil geology.


See: goergeyite.


A hexagonal mineral, K (sub 2) Ca (sub 4) Al (sub 2) Be (sub 4) Si (sub 24) O (sub 60) .H (sub 2) O ; osumilite group; forms colorless to greenish prisms. (Not millerite.)

mild and tough

Mellowed or ripened by weathering; said of brick clay; opposite of short and rough.

mild earth

Eng. Soft, loamy clay suitable for brickmaking, as opposed to stiffer clay below, which is suitable for making tiles and drainpipes. Kimeridge clay, Brill, Buckinghamshire.

mild steel

Steel that contains from 0.12% to 0.25% carbon. Also called low-carbon steel; soft steel. See also: yield stress.


A standard of resistance in wire. The resistance of 1 ft (30.5 cm) of wire that is 1 mil (25.4 mu m) in diameter.

milk of sulfur

See: colloidal sulfur.


A translucent, milk-white to green, yellow, or blue variety of common opal.

milky quartz

A milk-white, nearly opaque variety of quartz, commonly with a greasy luster. The milkiness is due to the presence of minute, fluid-filled inclusions. Syn: greasy quartz.


a. A mineral treatment plant in which crushing, wet grinding, and further treatment of ore is conducted. Also, separate components, such as ball mill, hammer mill, and rod mill. See also: ball mill; hammermill; rod mill; grinding mill; pug mill.

b. A passage connecting a stope or upper level with a level below, intended to be filled with broken ore that can then be drawn out at the bottom as desired for further transportation; an opening in the floor or bottom of a stope, through which the ore or mineral is passed or thrown downward along the footwall to the level. See also: glory hole. c. To fill a winze, or interior incline, with broken ore, to be drawn out at the bottom. d. A finishing plant where blocks of stone are sawed and trimmed. e. In quarrying, usually applied to the finishing plant where blocks are sawed into slabs; all other manufacturing processes are classed as shop work. f. An excavation made in the country rock, by a crosscut from the workings on a vein, to obtain waste for filling. It is left without timber so that the roof may fall in and furnish the required rock. g. Can. Reducing plant where ore is concentrated and/or metals are recovered. h. A single machine or a complete plant for rolling metals. i. See: cogging mill. j. To grind or cut away steel or iron with a toothed or serrated face bit; also, the tool so used. k. Eng. That part of an ironworks where puddle bars are converted into merchant iron; i.e., rolled iron ready for sale in bars, rods, or sheets. See also: forge. l. A preparation facility within which metal ore is cleaned, concentrated, or otherwise processed before it is shipped to the customer, refiner, smelter, or manufacturer. A mill includes all ancillary operations and structures necessary to clean, concentrate, or otherwise process metal ore, such as ore and gangue storage areas and loading facilities. m. By common usage, any establishment for reducing ores by other means than smelting. More strictly, a place or a machine in which ore or rock is crushed.

mill bar

A rough bar rolled or drawn directly from a bloom or puddle bar for conversion into merchant iron in the mill.

mill car

A car without a roof for carrying hoisting apparatus.


A metal object lost in a borehole that has been cut or ground away with a milling bit.

Miller-Bravais indices

A four-index type of Miller indices, useful but not necessary in order to define planes in crystal lattices in the hexagonal system; the symbols are hkil, in which i = -(h + k). CF: Miller indices.

Miller indices

Integers used to designate crystallographic planes. They are found as follows: (1) Determine where the plane intercepts each crystallographic axis in terms of multiples of the axial parameters; (2) take the reciprocals of these numbers and clear of fractions and common factors. These three numbers, designated (hkl), are the Miller indices for that plane. CF: Bragg indices; Miller-Bravais indices; crystal face; crystal indices; intercept. See also: symbols of crystal faces; indices of a crystal face.


A brass-yellow to bronze-yellow rhombohedral mineral: NiS. It usually has traces of cobalt, copper, and iron, and is often tarnished. Millerite generally occurs in fine hairlike or capillary crystals of extreme delicacy, chiefly as nodules in clay ironstone. Syn: capillary pyrite; nickel pyrite; hair pyrite. (Not milarite.)

mill feeder

In ore dressing, smelting, and refining, a laborer who regulates flow of ore, coke, flue scrapings, or other materials from bins, chutes, or belts into crushers, furnaces, or other equipment, or onto conveyor belts leading to equipment. Syn: conveyor-feeder operator.

mill furnace

A furnace for reheating iron that is to be rerolled, or welded, under a hammer.

millgrit rock

Som. Triassic dolomitic conglomerate.

mill head

a. Ore accepted for treatment in a concentrator, after any preliminary rejection such as waste removal.

b. Assay value, or units of value per ton, in ore accepted for treatment in a concentrating plant or mill.

mill-head grade

The grade of ore as it comes from a mine and goes to a mill.

mill-head ore

See: run-of-mill.

mill hole

An auxiliary shaft connecting a stope or other excavation with the level below. See also: mill; glory hole.


A prefix meaning one thousandth of. It divides a basic unit by 1,000, or multiplies it by 10 (super -3) ; abbrev., m. Commonly applied to units of measure in the metric and cgs systems; e.g., 1 mg = 0.001 g.


One-thousandth of an ampere; abbrev., mA.


One-thousandth of an angstrom; abbrev., mAa.


A unit of atmospheric pressure equal to one-thousandth of a bar or 1,000 dyn/cm (super 2) ; abbrev., mb.


A measure of gamma-ray exposure expressed as the product of the source in millicuries and the time of exposure in hours.


The customary unit of measurement of permeability, equal to one-thousandth of a darcy. See also: permeability. Abbrev., md.


A unit of temperature equal to one-thousandth of a degree; abbrev., mdeg.


One-thousandth of a farad; abbrev., mF.


a. A unit employed in the gravitational method of geophysical prospecting. It is about one millionth of the average value of the acceleration due to gravity at the Earth's surface; i.e., 1 milligal = 1 cm/s (super 2) .

b. A unit of acceleration used with gravity measurements; 10 (super -3) Gal = 10 (super -5) m/s (super 2) . Abbrev: mGal.


One-thousandth of a gauss; abbrev., mG.


A measure of gamma-ray exposure expressed as the product of the equivalent radium content of the source, in milligrams, and the time of exposure in hours.


One-thousandth of a henry; a unit of inductance; abbrev., mH.

millimeter screw micrometer

A precision caliper gage that measures the overall dimensions of unmounted fashioned gems more accurately but less conveniently than dial gages.


a. The grinding or crushing of ore. The term may include the operation of removing valueless or harmful constituents and preparation for market.

b. A combination of open-cut and underground mining, wherein the ore is mined in open cut and handled underground. It is underhand stoping applied to large deposits, wherein the ore is mined near the mouth of winzes or raises, and dropped by gravity to working levels below for transportation to the surface. Usually called glory-hole system. See also: mill. c. The act or process of cutting or grinding away a metal object lost in a borehole with a mill or milling bit.

milling bit

A bit equipped with hardened serrations or teeth used to grind or cut away metallic materials or junk obstructing a borehole. Also called rose bit. CF: junk mill.

milling grade

a. Ore containing sufficient recoverable value to warrant treatment.

b. S. Afr. An assumed average value of the ore sent to a mill, expressed as a percentage, or in pennyweights per short ton.

milling ore

a. Any ore that contains sufficient valuable minerals to be treated by any milling process. Syn: mill ore.

b. A dry ore that can be amalgamated or treated by leaching and other processes; usually these ores are low grade and free, or nearly so, from base metals.

milling width

Width of a lode that is designated for treatment in a mill, as calculated with regard to daily tonnage. Any excess broken during mining (stoping width) should be rejected before milling.

milling yield

S. Afr. The valuable material obtained from milling, expressed as a percentage or in pennyweights per short ton.


One-thousandth of a second; abbrev.: msec; ms.

millisecond delay

A type of delay cap with a definite but extremely short interval between the passing of current and the explosion.

millisecond-delay cap

A detonating cap that fires from 0.02 to 0.5 s after the firing current passes through it.

millisecond-delay detonator

See: short-delay detonator.


One-thousandth of a volt; abbrev., mV.


One who is employed in a mill, such as in an ore-dressing plant.

mill ore

See: milling ore.

mill roll

One of the rolls through which puddled iron is run prior to being marketed.

mill run

a. A given quantity of ore tested for its quality by actual milling; the yield of such a test.

b. Average, not esp. selected. c. In intermittent treatment of ore, with periodic cleanup, the period of such a run. Bulk test on a sample of ore during development of a treatment process.

mill sampler

A laborer who removes samples of crushed ore, concentrates, or tailings at various stages of processing, and puts them in labeled containers for laboratory analysis. Also called sampler.

mill scale

The scale of ferric oxide that peels from iron during rolling.

Mills-Crowe process

Method of regeneration of foul cyanide liquor from the gold leaching process. The barren solution is acidified, and gaseous hydrocyanic acid (HCN) is liberated, separated, and reabsorbed in an alkaline solution, such as lime water.

mill shoe

a. A shoe equipped with a hardened serrated cutting edge used to mill downward over and around a piece of drill-stem equipment lost in a borehole. See also: mill.

b. A shoe designed either to dress the down-hole tools for access to retrieve them, or to grind up the tool in a drill hole so that drilling can continue.


Term used in the slate industry to include all forms of structural slate used in exterior or interior construction.


A buhrstone; e.g., a coarse-grained sandstone or a fine-grained quartz conglomerate. Also, one of two thick disks of such material used for grinding grain and other materials fed through a center hole in the upper stone. Quarried underground in Virginia; also, produced in New York and (of granite) in North Carolina. See also: buhrstone.

millstone grit

Any hard, siliceous rock suitable for use as a material for millstones; specif. the Millstone Grit of the British Carboniferous, a coarse conglomeratic sandstone.

mill test

The determination of the metallic contents and recoverable metal in any given ore by the milling of a sufficient quantity to afford average milling conditions. See also: mill run.


Net tonnage of ore available for milling after eliminating waste and unpayable material.

mill value

S. Afr. The calculated value of ore before crushing. After treatment, there remains a residue of the valuable metal in the sands, slimes, or tailings, which, added to the yield obtained by treatment, should be equal to the mill value.


See: mimetite.


See: mimetite.


a. Said of crystals appearing to have a higher symmetry than their internal structure due to twinning, distortion, or interfacial angles at or close to a more symmetric form.

b. Said of crystals showing highly complex pseudosymmetry. CF: pseudosymmetry. c. A tectonite with a deformation fabric influenced by preexisting structural anisotropy; also the fabric itself.


A monoclinic mineral, Pb (sub 5) Cl(AsO (sub 4) ) (sub 3) ; apatite group, with arsenate replaced by phosphate; pseudohexagonal; resinous; sp gr, 7.3; in oxidized zones of lead-ore deposits. Syn: mimetesite; campylite; mimetene. CF: hedyphane.


See: end member.


A monoclinic mineral, VO(SO (sub 4) ).5H (sub 2) O ; a blue efflorescence at Minasragra, near Cerro de Pasco, Peru.


a. An opening or excavation in the ground for the purpose of extracting minerals; a pit or excavation from which ores or other mineral substances are taken by digging; an opening in the ground made for the purpose of taking out minerals, and in case of coal mines, commonly a worked vein; an excavation properly underground for digging out some usual product, such as ore, metal, or coal, including any deposit of any material suitable for excavation and working as a placer mine; collectively, the underground passage and workings and the minerals themselves.

b. A work for the excavation of minerals by means of pits, shafts, levels, tunnels, etc., as opposed to a quarry, where the whole excavation is open. In general, the existence of a mine is determined by the mode in which the mineral is obtained, and not by its chemical or geological character. The term also includes only excavations for their minerals or valuable mineral deposits. c. An excavation beneath the surface of the ground from which mineral matter of value is extracted. The word carries the sense of laborers working beneath a cover of ground and thus excludes oil, brine, and sulfur wells. Excavations for the extraction of ore or other economic minerals not requiring work beneath the surface are designated by a modifying word or phrase as: (1) opencut mine--an excavation for removing minerals that is open to the weather; (2) steam shovel mine--an opencut mine in which steam shovels or other power shovels are used for loading cars; (3) strip mine--a stripping; an opencut mine in which the overburden is removed from a coalbed before the coal is taken out; (4) placer mine--a deposit of sand, gravel, or talus from which some valuable mineral is extracted; and (5) hydraulic mine--a placer mine worked by means of a stream of water directed against a bank of sand, gravel, or talus; soft rock similarly worked. A quarry from which rock is extracted becomes a mine when it is carried under cover. Mines are commonly known by the mineral or metal extracted such as bauxite mines, copper mines, silver mines, coal mines, etc. d. The terms mine and coal mine are intended to signify any and all parts of the property of a mining plant, either on the surface or underground, that contribute directly or indirectly to the mining or handling of coal or ore. e. The term mine, as applied by quarrymen, is applied to underground workings having a roof of undisturbed rock. It is used in contrast with the open pit quarry. f. To dig a mine; to get ore, metals, coal, or precious stones out of the earth; to dig into, as the ground, for ore or metal; to work in a mine. g. An active mining area, including all land and property placed under, or above the surface of such land, used in or resulting from the work of extracting metal ore or minerals from their natural deposits by any means or method, including secondary recovery of metal ore from refuse or other storage piles, wastes, or rock dumps and mill tailings derived from the mining, cleaning, or concentration of metal ores.

mine atmosphere

The concentration of gases, including oxygen, that are present in a mine. Safe levels are maintained through ventilation. Measured at any point at least 12 in (30.5 cm) away from the back, face, rib, and floor in any mine.

mine bank

a. An area of ore deposits that can be worked by excavations above the water level.

b. The ground at the top of a mining shaft.

mine cage

semienclosed or fully enclosed models with a choice of sliding, folding, or rollup doors. Cages are used in either vertical or incline mine shafts. All cages are required to contain necessary safety features.

mine captain

a. A superintendent of a mine.

b. The director of work in a mine, with or without superior officials or subordinates. c. In metal mining, a foreman who supervises the extraction, hauling, and hoisting of ore in a mine. Also called ground boss.

mine car

One of the cars that are loaded at production points and hauled to the pit bottom or surface in a train by locomotives or other power. They vary in capacity, and are either of wood or steel construction or combinations of both. Mine cars have been classified into six kinds: (1) the solid or box type, which requires a rotary dump at the unloading terminal; (2) the rocker dump type, which has a V-shaped body rounded at the bottom; (3) the gable-bottom car, which is shaped like a capital W in cross section; (4) the Granby car, a special form of a side-dumping car; (5) bottom-dump cars; and (6) end-dump cars, which are commonly used for hand tramming in small mines. See also: drop-bottom car; endgate car; gable-bottom car; Granby car; solid car.

mine-car repairman

In anthracite coal mining; bituminous coal mining; metal mining; nonmetal mining, a person who repairs or replaces damaged parts of mine (pit) cars, such as axles, wheels, bodies, and couplings, by straightening, bolting, riveting, refitting, or making new parts as required. Also called car whacker; pit-car repairer.

mine characteristic

The relation between pressure, p, and volume, Q, in the ventilation of a mine. If the resistance, R, of the mine is known, then the mine characteristic can be expressed as p=RQ (super 2) . The curve of this equation for a particular mine may thus be plotted on the same axes as the characteristics of a fan. The point of intersection of this curve, termed the mine characteristic, with the pressure characteristic of the fan, indicates the pressure and volume at which the fan would work in ventilating that mine. Knowing the volume and pressure, the power and efficiency are obtained. The suitability of any fan to any mine can be studied, and the effect of possible changes in mine resistance may be predicted.

mine characteristic curve

As a graphical aid to the solution of problems in mine ventilation, the mine head (static and/or total) is often plotted against the quantity. This is called the mine characteristic curve, or simply the mine characteristic.

mine circulating fan

Mines create special problems in proper ventilation by their isolation from fresh air sources, and the presence of dangerous gases and dusts. Large fans are used for the stationary systems, while small portable types provide fresh air in dead-ends and other inaccessible locations. These fans may be driven by electricity or compressed air, and in addition to mine operations, are useful for work in manholes, pipe galleries, silos, tanks, vats, plane fuselages, ship holds, etc. The Mine Safety and Health Administration, Department of Labor can furnish specific recommendations concerning special problems.

mine committee

Representatives chosen by the union employees to confer with the representatives of the company; corresponds in mining to shop committees in manufacturing. Also called pit committee.

mine conveyor

See: underground mine conveyor.

mine cooling load

The total amount of heat, sensible and latent, which must be removed by the air in the working places.

mine development

The term employed to designate the operations involved in preparing a mine for ore extraction. These operations include tunneling, sinking, crosscutting, drifting and raising.

mine dial

See: miner's dial.

mine door

See: trapdoor; door.

mine drainage

See: drainage; drain tunnel; water hoist.

mined strata

In mine subsidence, the strata lying over the excavated area.

mine dust

a. Dust from rock drills, blasting, or handling rock.

b. In the quantity inhaled by workers, dust may be classified as dangerous, harmless, and borderline, although the classification is purely arbitrary. Silica is a dangerous dust and aluminum hydroxide is borderline. c. Scot. Calcined ironstone screenings. d. See: coal dust.

mined volume

In mine subsidence, the mined area multiplied by the mean thickness of the bed, or of that part of the bed that has been extracted.

mine examiner

See: fire boss.

mine expert

See: mining engineer.

mine fan

a. The main fan for a mine; normally situated at the surface.

b. A radial- or axial-flow ventilator. See also: fan; ventilation.

mine fan signal system

A system that indicates by electric light or electric audible signal, or both, the slowing down or stopping of a mine ventilating fan.

mine feeder circuit

A conductor or group of conductors, including feeder and sectionalizing switches or circuit breakers, installed in mine entries or gangways and extending to the limits set for permanent mine wiring, beyond which limits portable cables are used.

mine fill

See: hydraulic fill.

mine fire

This very dangerous occurrence may arise as the result of spontaneous combustion, the ignition of timbers by gob fires, electric cable defects, or the heating and ignition of conveyor belts due to friction.

mine fire truck

Designed to fight underground fires in mining operations, this low slung railcar is equipped with a water supply and pressure equipment for its fire hoses. When a fire occurs, the car can be sped to the scene along existing rails. The truck is capable of delivering hundreds of gallons of water, depending upon the size and model used.

mine foreman

a. The person charged with the responsibility of the general supervision of the underground workings of a mine and the persons employed therein. In certain states, the mine foreman is designated as the mine manager. See also: foreman.

b. Generally used to designate that company representative in complete 24-h charge of underground workings and legally held responsible for the safety and welfare of all underground employees. The foreman is generally State certified for competency. c. A deputy in metal mines. d. An official in charge of plant and associated labor on the surface, e.g., screen foreman.

mine ground

A stratum or group of strata containing layers of ironstone.


See: pithead.

mine head

In a mine ventilation system, the cumulative energy consumption is called the mine head. A head is in reality a pressure difference, determined in accordance with Bernoulli's principle.

mine hoist

A device for raising or lowering ore, rock, or coal from a mine and for lowering and raising workers and supplies. See also: hoist.

mine hoist control

This mechanism is designed to prevent accidents in mine cages caused by overspeeding in hoisting and lowering. It also prevents hoisting or lowering beyond the limits for which the controller is set. On electric hoists, it can apply a brake in case of power failure and may regulate brake speed in the event of an emergency stop.

mine inspector

a. Person who checks mines to determine the safety condition of working areas, equipment, ventilation, and electricity, and to detect fire and dust hazards.

b. Generally used as denoting the State mine inspector as contrasted to the Federal mine inspector. See also: inspector.

mine iron

Pig iron made entirely from ore; distinguished from cinder pig.

mine jeep

A special electrically driven car for underground transportation of officials, inspectors, repair, maintenance, and surveying crews and rescue workers.

mine lamp

Battery operated lamp; may be attached to a miner's cap to provide illumination in poorly lighted mine areas. Lamps are designed to focus on working areas when attached. A unit consists of a rechargeable battery, bulb, reflector, wires, etc. Mine lamps may be purchased outright or leased. Models include cap lamps, hand lamps, and trip lamps.

mine land reclamation

The process of transforming mine land into usable conditions; e.g., with regard to residential, recreational, agricultural, commercial or forestry purposes.

mine locomotive

A low, heavy, haulage engine, designed for underground operation; usually propelled by electricity, gasoline, or compressed air. See also: electric mine locomotive; trolley locomotive.

mine mason

Mineworker who lines the galleries and other rooms with masonry, works on the repair of mine supports, and builds ventilation doors and dams.

mine motorman

See: motorman.

mine opening

See: opening.

mine power center

A mine power center is a combined transformer and distribution unit complete within a metal enclosure, usually of explosion-proof design, from which one or more low-voltage power circuits are taken.

mine prop

Section of wood, generally part of a small tree trunk, used for holding up rock in the roof of a mine.


a. In anthracite and bituminous coal mining, one who performs the complete set of duties involved in driving underground openings to extract coal, slate, and rock, with a hand or machine drill, into which explosives are charged and set off to break up the mass. Also called coal digger; coal getter; coal hewer; digger; faceman.

b. In nonmetal mining, such as limestone, one who drills holes in working face of a limestone mine, and inserts and sets off charges of explosives in holes. May be designated as development miner when working in new areas to drive drifts, shafts, sumps, and entry areas into stopes; high-raise miner when working in vertical areas to gain access into new development areas; or stope miner when working in horizontal openings in limestone strata. Syn: stope miner. c. In mining, one who performs the complete set of duties involved in driving underground openings to extract ore or rock: drills holes in working face of ore or rock, with a hand or machine drill; inserts explosives in drill holes and sets them off to break up the mass; shovels ore or rock into mine cars or onto a conveyor, and pushes mine cars to haulageways, where they are hauled by draft animals, mine locomotive (motor), or haulage cable to the surface, or to the shaft bottom for hoisting; and installs timbering to support the walls and roof, or for chutes or staging. Due to standardization of mining methods and development of mining machinery, these jobs may be performed by several workers. Where conditions are favorable, loading is done by machine. d. One who mines; such as (1) a person engaged in the business or occupation of getting ore, coal, precious substances, or other natural substances out of the earth; (2) a machine for automatic mining (as of coal); and (3) a worker on the construction of underground tunnels and shafts (as for roads, railways, waterways). e. A worker in a coal mine who is paid a certain price for each ton of coal he or she digs or blasts from the solid seam, as distinguished from the laborer who loads the cars, etc. The miner's helpers load the coal; they are also called laborers. f. Includes all laborers who work in a mine, whether digging coal, timbering, or making places safe. g. Loosely used to designate all underground employees; technically, and in many cases legally, only those who have served an apprenticeship as helpers or those who are State licensed as miners. h. A worker who cuts coal in a breast or chamber by contract; the highest-skilled worker of a colliery. i. One who mines; a digger for metals and other minerals; is not necessarily a mechanic, handcraftsman, or artisan, and the term imports neither learning nor skill. j. Abbrev. for continuous miner.


See: ore microscopy.


a. A naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties. CF: metallic.

b. In miner's phraseology, ore. See also: ore. c. See: mineral species; mineral series; mineral group. d. Any natural resource extracted from the earth for human use; e.g., ores, salts, coal, or petroleum. e. In flotation, valuable mineral constituents of ore as opposed to gangue minerals. f. Any inorganic plant or animal nutrient. g. Any member of the mineral kingdom as opposed to the animal and plant kingdoms.

mineral acre

The full mineral interest in 1 acre (0.4 ha) of land.

mineral adipocire

See: hatchettite.

mineral assessment

a. The process of appraisal of identified and undiscovered mineral resources within some specified region, and the product of that appraisal.

b. The estimation of mineral endowment, meaning the number of deposits or the tonnage of metal that occurs in the region, given some minimum size of accumulation (deposit), minimum concentration (grade), and maximum depth of occurrence. Syn: predictive metallogeny.

mineral association

A group of minerals found together in a rock, esp. in a sedimentary rock.

mineral belt

An elongated region of mineralization; an area containing several mineral deposits.

mineral blossom

Drusy quartz.

mineral bruto

Sp. Raw ore.

mineral caoutchouc

See: elaterite; helenite.

mineral carbonatado

Sp. Carbonate ore.

mineral charcoal

a. A pulverulent, lusterless substance, showing distinct vegetal structure, and containing a high percentage of carbon with little hydrogen and oxygen, occurring in thin layers in bituminous coal. Called mother of coal by miners.

b. Another name for fusain.

mineral claim

A mining claim.

mineral cleavage

Mineral breakage along specific crystallographic planes in all specimens due to fewer or weaker chemical bonds in those directions. CF: mineral parting.

mineral deed

A conveyance of an interest in the minerals in, on, or under a described tract of land. The grantee is given operating rights on the land; easements of access to the minerals are normally implied unless expressly negated.

mineral de fusion propia

Sp. Self-fluxing ore.

mineral deposit

a. A mass of naturally occurring mineral material; e.g., metal ores or nonmetallic minerals, usually of economic value, without regard to mode of origin. Accumulations of coal and petroleum may or may not be included; usage should be defined in context. Syn: orebody.

b. A mineral occurrence of sufficient size and grade that it might, under favorable circumstances, be considered to have economic potential. See also: ore; ore deposit.

mineral deposit model

The systematically arranged information describing the essential attributes (properties) of a class of mineral deposits. The model may be empirical (descriptive), in which instance the various attributes are recognized as essential even though their relationships are unknown; or it may be theoretical (genetic), in which instance the attributes are interrelated through some fundamental concept. See also: model.

mineral dresser

A machine for trimming or dressing mineralogical specimens.

mineral dressing

a. Physical and chemical concentration of raw ore into a product from which a metal can be recovered at a profit.

b. Treatment of natural ores or partly processed products derived from such ores in order to segregate or upgrade some or all of their valuable constituents, and/or remove those not desired by an industrial user. Mineral dressing processes are applied to industrial wastes to retrieve useful byproducts. See also: mineral processing; ore dressing.

mineral economics

Study and application of the technical and administrative processes used in management, control, and finance connected with the discovery, development, exploitation, and marketing of minerals.

mineral endowment

The physical aggregate of mineral occurrences in a region above some lower cutoff.

mineral engineering

Term covers a wide field in which many resources of modern science and engineering are used in discovery, development, exploitation, and use of natural mineral deposits.

mineral entry

The filing of a claim for public land to obtain the right to any minerals it may contain.

mineral facies

See: metamorphic facies.

mineral fat

See: ozocerite.

mineral fiber

a. Fibrous mineral whose fibers are longer than 5 mu m and with an aspect ratio (length over width) equal to or greater than 3:1 as determined by the membrane filter method at 400X to 500X magnification (4-mm objective) phase contrast illumination.

b. The smallest elongated crystalline unit that can be separated from a bundle or appears to have grown individually in that shape, and that exhibits a resemblance to organic fibers.

mineral field

Scot. A tract of country in which workable minerals are found; a mineral leasehold.

mineral filler

A finely pulverized inert mineral or rock that is included in a manufactured product--e.g., paper, rubber, and plastics--to impart certain useful properties, such as hardness, smoothness, or strength. Common mineral fillers include asbestos, kaolin, and talc.

mineral fuel

Coal or petroleum. See also: fossil fuel.

mineral group

Two or more mineral species having identical or closely related structures; e.g., hematite group or zeolite group. See also: mineral.

mineral interests

Mineral interests in land means all the minerals beneath the surface. Such interests are a part of the realty, and the estate in them is subject to the ordinary rules of law governing the title to real property.

mineral inventory

An accounting of the mineral reserves and resources contained in known mineral deposits including inactive mines, operating mines, and undeveloped sites.


The process or processes by which a mineral or minerals are introduced into a rock, resulting in a valuable or potentially valuable deposit. It is a general term, incorporating various types; e.g., fissure filling, impregnation, and replacement.


To convert to a mineral substance; to impregnate with mineral material. The term is applied to the processes of ore formation and also to the process of fossilization.

mineralized bubble

In flotation, one of the bubbles that rise from the pulp loaded with particles of desired mineral.


See: ore-forming fluid; geologic mineralizer.

mineralizing agent

See: ore-forming fluid; geologic mineralizer.

mineral land

Land that is worth more for mining than for agriculture. The fact that the land contains some gold or silver would not constitute it mineral land if the gold and silver did not exist in sufficient quantities to pay to work. Land not mineral in character is subject to entry and patent as a homestead, however limited its value for agricultural purposes. CF: stone land.

Mineral Lands and Mining

The leasable minerals include oil, gas, sodium, potash, phosphate, coal, and all minerals within acquired lands. Acquisition is by application for a Government lease and permits to mine or explore after lease issuance.

mineral lease

See: mining lease.

mineral occurrence

a. The presence of useful minerals or rocks in an area under examination.

b. A concentration of a mineral (usually, but not necessarily, considered in terms of some commodity, such as copper, barite, or gold) that is considered to be valuable or that is of scientific or technical interest. In rare instances (such as titanium in a rutile-bearing black sand), the concentration of the commodity might be less than its average crustal abundance.

mineralogical guide

A mineral that is present near an orebody and is related to the processes of ore deposition. Guides help locate ore and may constitute targets for ore search.

mineralogical phase rule

Any of several modifications of the fundamental Gibbs phase rule, taking into account the number of degrees of freedom consumed by the fixing of physical-chemical variables in the natural environment. The most famous such rule, that of Goldschmidt, assumes that two variables (taken as pressure and temperature) are fixed externally and that consequently the number of phases (minerals) in a system (rock) will not generally exceed the number of components. The Korzhinskii-Thompson version takes into account the external imposition of chemical potentials of perfectly mobile components, and thereby reduces the maximum expectable number of minerals in a given rock to the number of inert components. Syn: Goldschmidt's phase rule.


Person who studies the formation, properties, use, occurrence, composition, and classification of minerals; a geologist specialized in mineralogy. Syn: oryctologist (obsolete).


See: ore microscopy.


The study of minerals: formation, occurrence, use, properties, composition, and classification. Adj. mineralogic, mineralogical.


Minerallike constituent of rocks which is not definite enough in chemical composition or in physical properties to be considered a mineral. Hydrocarbons, volcanic glass, and palagonite are classed as mineraloids.

mineral paint

See: mineral pigment.

mineral parting

Mineral breakage along specific crystallographic planes in some specimens due to twinning, exsolution lamellae, or chemical alteration. See also: parting. CF: mineral cleavage.

mineral pigment

A mineral material used to give color, opacity, or body to a paint, stucco, plaster, or similar material. See also: ocher; sienna; umber.

mineral processing

The dry and wet crushing and grinding of ore or other mineral-bearing products for the purpose of raising concentrate grade; removal of waste and unwanted or deleterious substances from an otherwise useful product; separation into distinct species of mixed minerals; chemical attack and dissolution of selected values. Among the methods used are hand sorting (including radioactivation and fluorescence); dense media separation; screening and classification; gravity treatment with jigs, shaking tables, Humphries spirals, Frue vanners, or sluices; magnetic separation at low or high intensity; leach treatment, perhaps using pressure and heat; and (universally) froth flotation. Also called beneficiation; ore dressing; mineral dressing.

mineral province

A region in which the source, age, and regional distribution of a complex of minerals in a sediment are related.

mineral reserves

See: reserves.

mineral resin

Any of a group of resinous, usually fossilized, mineral hydrocarbon deposits; e.g., bitumen and asphalt. See also: resin.

mineral right

The ownership of the minerals under a given surface, with the right to enter thereon, mine, and remove them. It may be separated from the surface ownership, but, if not so separated by distinct conveyance, the latter includes it.

mineral rubber

See: uintaite.

mineral salt

Mined rock salt, halite.

mineral sequence

The sequential order of mineral deposition during formation of an ore deposit. CF: paragenesis.

mineral series

Mineral species showing continuous variation in their properties with change in composition. A series may be complete; e.g., tennantite-tetrahedrite, or partial; e.g., iron replacing zinc in sphalerite. Syn: crystal solution; solid solution. See also: mineral.

mineral species

a. Any mineral that can be distinguished from all other minerals by current determinative methods. b. A naturally occurring homogeneous substance of inorganic origin, in chemical composition either definite or ranging between certain limits, and possessing characteristic physical properties and usually a crystalline structure. See also: mineral.

mineral spring

A spring whose water contains enough mineral matter to give it a definite taste, in comparison to ordinary drinking water, esp. if the taste is unpleasant or if the water is regarded as having therapeutic value. This type of spring is often described in terms of its principal characteristic constituent; e.g., salt spring.

minerals separation process

A flotation process based on surface-tension phenomena, accelerated by means of addition to the pulp of small quantities of oil and air in minute subdivision. Only about 0.1% oil is added, and the pulp is violently agitated for 1 to 10 min. Innumerable small bubbles of air are thus mechanically introduced, which join the oil-coated particles. These are then removed in a spitzkasten. Exposure to the air after this treatment then aerates any mineral that has not already taken up its oil film, after which a second spitzkasten treatment removes this. An early name for froth flotation.

mineral stabilizer

A fine, water-insoluble, inorganic material, used in admixture with solid or semisolid bituminous materials.

mineral streaking

In metamorphic rocks, lineation of grains of a mineral. Syn: streaking.

mineral tallow

See: hatchettine; hatchettite. Also called mountain tallow.

mineral tar

a. Tar derived from various bituminous minerals, such as coal, shale, peat, etc. Shale tar. Syn: mountain tar.

b. See: maltha; pittasphalt.

mineral turquoise

Term to distinguish true turquoise from odonotolite (bone turquoise).

mineral variety

Specimens of a mineral species with distinctive physical properties due to: (1) specific history; e.g., Iceland spar, a coarsely crystalline variety of calcite of optical grade, or (2) small chemical variation; e.g., amalgam, a mercurian variety of native silver.

mineral vein

See: vein.

mineral water

Water that contains an unusually high percentage of some mineral substance that gives the water a distinctive taste and sometimes other properties. Considered to be beneficial in the treatment of various ailments. Also called spa water.

mineral wax

See: ozocerite.

mineral wedging

A form of chemical weathering resulting in the formation of new minerals that have greater aggregate volumes than the old ones. These expanding minerals then act as wedges to split adjacent minerals and rocks apart.

mineral wool

A substance outwardly resembling wool, presenting a mass of fine interlaced filaments. It is made by subjecting furnace slag or certain rocks, while molten, to a strong blast. Being both insect proof and fireproof, it forms a desirable packing for walls, a covering for steam boilers, etc. Also called mineral cotton, silicate cotton, and slag wool. Syn: glass wool.

mineral zoning

See: zoning of ore deposits.

mine refuse

a. Waste material in the raw coal that has been removed in a cleaning or preparation plant.

b. Notably used to describe colliery rejects; also called tailings.

mine rescue apparatus

The rescuing of miners overcome by a mine fire, or trapped in workings by an explosion, necessitates the use of apparatus that will enable the rescue team to work in irrespirable or poisonous gases. The equipment used is known as mine rescue apparatus. See also: rescue apparatus.

mine rescue car

One of a number of railway cars specially equipped with mine rescue apparatus, safety lamps, first-aid supplies, and other materials, maintained by the Mine Safety and Health Administration in various sections of the United States. These cars serve as movable stations for the training of miners in the use of mine rescue apparatus, and in first aid to the injured; as centers for the promotion of mine safety; as emergency stations for assisting at mine fires, explosions, or other disasters. Similar cars are maintained by a number of mining companies. Syn: mine-safety car.

mine rescue crew

A crew consisting usually of five people who are thoroughly trained in the use of mine rescue apparatus, and are capable of wearing it in rescue or recovery work in a mine following an explosion, or to combat a mine fire.

mine rescue lamp

A name given to a particular type of electric safety hand lamp used in rescue operations. It is equipped with a lens for concentrating or diffusing the light beam as occasion may require.

mine resistance

a. The resistance offered by a mine to the passage of an air current. The mine resistance is due to the friction of the air rubbing along the sides, top, and bottom of the air passages. To overcome this friction, the total ventilating pressure must be applied against the airway and this pressure must be equal to the mine resistance. Mine resistance is caused by the dragging of the air against the mine surfaces and other obstructions. The rougher the mine surfaces and the more the obstructions, the greater the resistance to the flow of air.

b. Includes any natural ventilation effect present and is calculated from air volume and total pressure. The standard practice in the United Kingdom is to express the resistance of a mine in square feet of equivalent orifice.

mine road

Any mine track used for general haulage.

mine roadway area measurement

See: tape-triangulation method.

mine rock

A more or less altered rock found in ore channels. Gangue.


The study of mineral associations in the broadest sense, such as the correlation of igneous rocks or magmatic provinces with their ore deposits.


The origin and growth of minerals.

minerogenetic epoch

See: metallogenetic epoch.

minerogenetic province

a. An area in which mineralization has been active at one or more periods. If the mineralization has been chiefly metalliferous, the term metallogenetic is applicable. Syn: metallogenetic province.

b. A region characterized by relatively abundant mineralization dominantly of one type.


The row of drill holes in a tunnel face, located below the breaking-down holes.

miner's bar

An iron bar pointed at one end, chisel-edged at the other, used in coal mining.

miner's box

A wood or iron box located in or near the working place of a miner in which tools, supplies, etc. are kept. Required by law in some States.

miner's dial

An underground surveying instrument for measuring and setting out angles and determining magnetic north. Syn: mine dial.

miner's dip needle

A portable form of dip needle used for indicating the presence of magnetic ores. Also called dipping compass.

miner's electric cap lamp

a. A lamp for mounting on a miner's cap and receiving electric energy through a cord which connects the lamp with a small battery.

b. An electric lamp designed for fixing to a miner's helmet. Its principal parts are: (1) the battery, either lead acid or alkaline; (2) the headpiece, of plastic or aluminum alloy, with switch; and (3) a length of twin-cord cable covered with tough rubber or with neoprene--a fire- and acid-resisting substitute. The lead-acid lamps commonly use either a 4-V, 1.0-A bulb with a light output of about 47.5 lumens or else a 4-V, 0.8-A bulb of 38 lumens output. The headpiece is equipped with an auxiliary, 4 V, 0.46-A bulb.

miner's hammer

A hammer for breaking ore.

miner's hand lamp

A self-contained mine lamp with a handle for convenience in carrying.

miner's hard cap

Cap made of rigid, strong materials such as vulcanized fiber, glass fiber or plastic, which protects a worker from injury caused by falling objects, large chips, or by striking the head against projecting materials. The cap has a cradle to cushion the shock of blows and a sweat band to absorb perspiration; it is water resistant and nonconductive. A front visor shields the face and eyes from overhead glare, and makes the cap suitable for wear in close, confined spaces where a full brim might interfere.

miner's helmet

A hat designed for miners to provide head protection and for holding the cap lamp. See also: miner's hard cap.

miner's horn

A horn or metal spoon used to collect ore particles in gold washing.

miner's inch

a. The rate of flow of water through an aperture 1 in (2.54 cm) square under a given pressure, generally taken to be that of water standing 6 in (15.2 cm) above the top of the aperture. It is not a universal value but is fixed by statute in several States. A commonly accepted rate is 90 ft (super 3) /h (2.5 m (super 3) /h), or 1-1/2 ft (super 3) /min (0.042 m (super 3) /min). CF: sluice head.

b. A unit used in California, around 1900, for measuring water flow in hydraulicking. It represented the outflow from a 1-in (super 2) (6.5-cm (super 2) ) opening in the side of a box. It varied from 2,000 to 2,600 ft (super 3) /per day (56.6 to 73.6 m (super 3) /d), according to the height of water, etc. c. The term is not definite without specification of the head or pressure. It has no fixed meaning and in one locality sometimes is a very different quantity according to miner's measurement in another locality. It has been defined as the amount of water that will pass in 24 hours through an opening 1 in (2.54 cm) square under a head of 6 in.

miner's inch day

Flow of 1 miner's inch for 24 hours.

miner's lamp

a. In nongassy mines, acetylene lamps and various electric lamps; in gassy mines, approved flame safety lamps, electric hand or cap lamps.

b. Any one of a variety of lamps used by a miner to furnish light; e.g., oil lamps, carbide lamps, flame safety lamps, electric cap lamps, etc.

miner's lung

See: pneumoconiosis.

miner's needle

A long, slender, tapering, metal rod left in a hole when tamping and afterwards withdrawn, to provide a passage, to the blasting charge, for the squib.

miners' nystagmus

An occupational disease that occurs among coal miners, usually those of middle age or elderly, who have worked for a period of 25 to 30 years underground. Its physical symptoms consist of difficulty of seeing in the dark or in poor light, excessive sensitivity to and intolerance of glare, and a rhythmic oscillation of the eyeballs. As a result of these oscillations, there may be apparent movement of the objects looked at and defective visual acuity. Associated with these ocular symptoms are other general disorders, such as headaches and dizziness, particularly after stooping or bending, and the development of psychoneurotic symptoms is common in the later stages of the disease. If the disease is not checked, the nervous disorders may become so severe as to render the miner totally disabled.

miners' oil

An oil, producing little smoke, used in miners' wick-fed open lamps.

miner's pan

See: pan.

miner's pick

See: pick.

miners' rescue party

A team of trained mine rescue workers, from five to eight strong; they operate after explosions, and during and after mine fires. See also: rescue team.

miner's right

a. An annual permit from the Government to occupy and work mineral land.

b. In California, the right of a miner to dig for precious metals on public lands, occupied by another for agricultural purposes.

miners' rules

Rules and regulations proclaimed by the miners of any district relating to the location, recording, and the work necessary to hold possession of a mining claim. It was the miners' rules of the early days of the mining industry that were the basis of the present laws. The local mining laws and regulations of 1849 and later are given in vol. 14, 10th Census of the United States, 1880, compiled by Clarence King.

miner's self-rescuer

A small form of breathing apparatus for protection against carbon monoxide, worn on a miner's belt. It consists of a canister with a mouthpiece directly attached to it. The wearer breathes through the mouth, the nose being closed by a clip. The canister contains a layer of fused calcium chloride to absorb the water vapor in the air which destroys the efficiency of the other chemical called hopcalite. The self-rescuer affords protection for 30 min, so that miners surviving an explosion may walk out through a mine atmosphere that contains sufficient oxygen but also a fatal percentage of carbon monoxide.

miner's wedge

A metallic wedge or plug for splitting off masses of coal.

miner's weight

The term used in a coal mining lease as the basis for the price per ton to be paid for mining. It is not a fixed, unvarying quantity of mine-run material, but is such a quantity of material as operators and miners may, from time to time, agree as being necessary or sufficent to produce a ton of prepared coal.

mine run

a. The entire unscreened output of a mine. Also called run-of-mine.

b. The product of the mines before being sized and cleaned. c. A product of common or average grade.

mine-run coal

Ungraded coal of mixed sizes as it comes from the mine.

mine-run mica

See: book mica.

mine-safety car

See: mine rescue car.

mine signal system

Designed esp. for use in mines, these signal lights at individual switches immediately indicate to the motorman whether or not it is safe to proceed. Green and amber lights work automatically with the movement of the switches. May be used with locally controlled switches, or with those operated by a central dispatcher.

mine skip

Skip used to bring mined material to the surface of a mine shaft; manufactured in various sizes and designs for both vertical and incline shafts, including tipover models and bottom door dump models.

mine static head

The energy consumed in the ventilation system to overcome all flow head losses. It includes all the decreases in total head (supplied from static head) that occur between the entrance and discharge of the system.

mine superintendent

A mine manager or group manager.

mine surveyor

The official at a mine who periodically surveys the mine workings and prepares plans for the manager. Formerly, the mine surveyor carried out many of the duties now performed by the planning department. See: surveyor; mine.

mine tin

Tin obtained from veins or lodes, as distinguished from stream tin.

mine tons

Gross tonnage of ore including waste and unpayable material.

mine total head

The sum of all energy losses in the ventilation system. Numerically, it is the total of the mine static and velocity heads. See also: total ventilating pressure; ventilating pressure.

mine track device

One of a variety of track devices to provide maximum safety for haulage trains in mines. Designed to be used in conjunction with switch signals, these devices include electric switch throwers operated by hand contractors on a copper plate, overhead hand controllers, remote control, or trolley contractors. Other safety equipment includes mechanical switches for gaseous or hot mines, derailing switches for trains out of control, and automatic mine-door opening devices.

mine tractor

A trackless, self-propelled vehicle used to transport equipment and supplies and for general service work. See also: tractor.

mine valuation

Properly weighing the financial considerations to place a present value on mineral reserves.

mine velocity head

The velocity head at the discharge of the ventilation system. Throughout the system, the velocity head changes with each change in duct area or number and is a function only of the velocity of airflow. It is not a head loss. The velocity head for the system must technically be counted a loss, because the kinetic energy of the air is discharged to the atmosphere and wasted. Therefore, it must be considered a loss to the system in determining overall energy loss.

mine ventilating fan

A motor-driven disk, propeller, or wheel for blowing (or exhausting) air to provide ventilation of a mine. See also: ventilation. Syn: ventilating fan.

mine ventilation auxiliary fan

A small fan installed underground for ventilating coal faces or hard rock headings that are not adequately ventilated by the air current produced by the mine-ventilation fan. An auxiliary fan is usually from 0.5 to 1.0 m in diameter. It is driven by compressed air or electricity. The auxiliary fan can be used to force or exhaust ventilate the workplace.

mine-ventilation fan

A machine possessing rotating air-moving blades to exhaust or push the air volume necessary to ventilate mine workings. See also: aerofoil-vane fan; axial-flow fan.

mine-ventilation fan characteristics

The behavior of a fan under various conditions cannot be expressed in simple mathematics but may be shown graphically by suitable curves, known as the fan's characteristic curves or characteristics. The curves of interest are generally head versus air quantity, power versus air quantity, and efficiency versus air quantity.

mine ventilation system

An arrangement of connecting airways in a mine together with the pressure sources and control devices that produce and govern airflow.

mine water

Water pumped from mines usually contains impurities, some of which are in suspension, but the majority, which are soluble, cause the water to be hard. The water often contains corrosive agents, such as acids or alkalis.

mine wireman

See: wireman.


Ancient subterranean passages or mine excavations.

mingled ground

Mixed clay and sand or rock.


A monoclinic mineral, K (sub 3) Fe(C (sub 2) O (sub 4) ) (sub 3) .3H (sub 2) O ; green; an oxalate.

miniature current meter

A device used to measure the passage of current past a probe on each blade of a propeller type, or each cup of a price-type meter by detecting the change of electrical resistance between that probe and a distant electrode.

minimum deviation

A method for measuring the refractive index of a prism or a liquid in a hollow prism by determining the minimum deflected angle of a light beam.

minimum firing current

As applied to electric blasting caps, the limit below which firing will not occur.

minimum ignition energy

The minimum ignition energy required for the ignition of a particular flammable mixture at a specified temperature and pressure.

minimum oxygen content

The U.S. Mine Safety and Health Administration and other recognized safety and health agencies recommend 19.5% as the minimum oxygen content allowable.

minimum product firing temperature

The lowest product temperature at which an explosive or explosive unit is approved for use.


The science, technique, and business of mineral discovery and exploitation. Strictly, the word connotes underground work directed to severance and treatment of ore or associated rock. Practically, it includes opencast work, quarrying, alluvial dredging, and combined operations, including surface and underground attack and ore treatment. CF: mining geology; mining engineering.

mining advancing

A method of mining by which the ore or coal is mined as the excavation advances from the shaft or main opening. CF: mining retreating.

mining camp

a. A colony of miners settled temporarily near a mine or a goldfield.

b. A term loosely applied to any mining town.

mining captain

Person in charge of mining operations.

mining case

A frame of a shaft, or gallery, composed of four pieces of plank.

mining claim

a. That portion of the public mineral lands that a miner, for mining purposes, takes hold of and possesses in accordance with mining laws.

b. A mining claim is a parcel of land containing valuable minerals in the soil or rock. A location is the act of appropriating such a parcel of land according to law or to certain established rules. See also: claim; placer claim; location. c. In the General Mining Law of 1872, that portion of a vein or lode and of the adjoining surface, or of the surface and subjacent material to which a claimant has acquired the right of possession by virtue of a compliance with such statute and the local laws and rules of the district within which the location may be situated. Independent of acts of the U.S. Congress providing a mode for the acquisition of title to the mineral lands of the United States, the term has always been applied to a portion of such lands to which the right of exclusive possession and enjoyment by a private person or persons, has been asserted by actual occupation, and compliance with the mining laws and regulations. Syn: holding. d. Distinction between mining claim and location is that they are not always synonymous and may often mean different things; a mining claim may refer to a parcel of land containing valuable mineral in its soil or rock, while location is the act of appropriating such land according to certain established rules. A mining claim may include as many adjoining locations as the locator may make or purchase, and the ground covered by all, though constituting what is claimed for mining purposes, will constitute a mining claim and will be so designated. e. Title issued by the Government concerned to an individual or group, which grants that individual or group the right to exploit mineral wealth in a specified area by approved methods in accordance with the ruling laws and regulations. f. A claim on mineral lands.

mining compass

An instrument giving qualitative indications of anomalies in the magnetic field.

mining dial

See: dial.

mining disaster

An accident in a mine in which a large number of people are killed. See also: major mine disaster.

mining disease

See also: anthracosis; infective jaundice; nystagmus; pneumoconiosis; silicosis; simple silicosis.

mining district

A section of country usually designated by name, having described or understood boundaries within which minerals are found and worked under rules and regulations prescribed by the miners therein. There is no limit to its territorial extent and its boundaries may be changed if vested rights are not thereby interfered with.

mining ditch

A ditch for conducting water used in mining. CF: mining sluice.

mining engineer

a. A person qualified by education, training, and experience in mining engineering.

b. If qualified and of standing in the profession, 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. Usually a specialist in one or more branches of work. Activities may include prospecting, surveying, sampling and valuation, technical underground management, milling, assaying, ventilation control, layout of workings and plant, geological examination, and company administration. c. One versed in, or one who follows, as a calling or profession, the business of mining engineering. Graduates of technical mining schools are given the degree of engineer of mines and authority to sign the letters E.M. after their names.

mining engineering

The planning and design of mines, taking into account economic, technical, and geologic factors; also supervision of the extraction, and sometimes the preliminary refinement, of the raw material. CF: mining; mining geology.

mining explosive

One of the high explosives used for mining and quarrying. They can be divided into four main classes: gelatins; semigelatins; nitroglycerin powders, and non-nitroglycerin explosives, including water gels, emulsions, and ANFO.

mining ground

a. The study of geologic structures and particularly the modes of formation and occurrence of mineral deposits and their discovery. Syn: ore geology.

b. In coal mining, the study of: rock formations, particularly with reference to the Carboniferous System; the mode of formation of coal seams, their discovery and correlation. See also: geology. c. The study of the geologic aspects of mineral deposits, with particular regard to problems associated with mining. CF: mining; mining engineering. �= ��Q ��Q M�� � � {�DICTIONARY TERMS:mining ground No land can be a mining claim unless No land can be a mining claim unless based upon a location; otherwise it may be mining ground or a mine. For instance, the bed of a navigable river is not subject to mining location, but if mining is conducted thereon by dredging, it is mining ground; or, where land is covered by an agricultural patent and worked for its mineral deposits, it is mining ground and not a mining claim. Hence, land from which a mineral substance is obtained from the earth by the process of mining may, with propriety, be called mining ground or mining land. See also: claim; location.

mining hazard

Any of the dangers peculiar to the winning and working of coal and minerals. These include collapse of ground, explosion of released gas, inundation by water, spontaneous combustion, inhalation of dust and poisonous gases, etc.

mining head

The mechanism on a continuous mining machine that breaks down the coal.

mining lease

A legal contract for the right to work a mine and extract the mineral or other valuable deposits from it under prescribed conditions of time, price, rental, or royalties. Syn: mineral lease.

mining locomotive

A small locomotive for use in underground haulage, sometimes consisting of a car bearing a powerful electric motor, built very low and operated through a trolley. May also be operated by electricity from batteries.

mining machine

A coal-cutting machine.

mining machine operator

See: machine miner.

mining-machine-operator helper

See: machine helper.

mining machine truck

A truck used for transporting shortwall mining machines. Track-mounted trucks are necessarily limited in use to sections employing track. Crawler-type trucks are capable of transporting the cutting machine without need of track and without benefit of ropes.

mining method

Any of the systems employed in the exploitation of coal seams and orebodies. The method adopted depends on a large number of factors, mainly, the quality, shape, size, and depth of the deposit; accessibility and capital available. See also: coal mining methods; metal mining; stoping methods.

mining ore from top down

See: top slicing and cover caving.

mining property

Property, esp. land, valued for its mining possibilities.

mining purposes

The term "mining purposes" as used in connection with mill-site locations, is very comprehensive, and may include any reasonable use for mining purposes that the quartz lode mining claim may require for its proper working and development. This may be very little, or it may be a great deal. The locator of a quartz lode mining claim is required to do only $100 worth of work each year until obtaining a patent.

mining recorder

In a mining camp, a person selected to keep a record of all mining claims and properties.

mining retreating

A process of mining by which the ore, or coal, is untouched until after all the gangways, etc., are driven, when the work of extraction begins at the boundary and progresses toward the shaft. CF: mining advancing.

mining right

Upon a specific piece of ground, a right to enter upon and occupy the ground for the purpose of working it, either by underground excavations or open workings, to obtain from it the mineral ores which may be deposited therein.

mining shield

A cover or canopy developed by the U.S. Bureau of Mines for the protection of mine workers and machines at the face of a mechanized coal heading. Hydraulic rams telescope and steer the shield forward as the face advances. It enables continuous miners to operate with greater safety.

mining sluice

An artificial channel or passage for water used in mining. CF: mining ditch.

mining system

Work, as it is commenced on the ground, is such that, if continued, will lead to a discovery and development of the veins or orebodies that are supposed to be in the claim, or, if these are known, that the work will facilitate the extraction of the ores and minerals.

mining theodolite

A theodolite having particular features of design that make it suitable as an underground surveying instrument; e.g., incorporating an arrangement for the centering movement to be above the foot screws.

mining title

A claim, exclusive prospecting license, concession, right, or lease. A grant under laws and mining regulations to a person or group of approved persons of the right to develop and exploit a properly delineated area for its mineral wealth.

mining-type visibility meter

An instrument to facilitate observation of the essential elements of visual tasks in coal mines. It is a brightness meter in which the comparison field is illuminated by a cap lamp headpiece attached outside the instrument. No internal electrical circuit exists other than that which connects the photocell to the microammeter and the meter can therefore be used anywhere in a safety-lamp mine without restrictions.

mining under

The act of digging under coal or in a soft strata in coal seams.

mining width

The minimum width necessary for the extraction of ore regardless of the actual width of ore-bearing rock. See also: stoping width.


The siftings of iron ore after calcination.


A tetragonal mineral, Pb (sub 3) O (sub 4) ; red; an alteration product of galena or cerussite. Syn: red lead.


A monoclinic mineral, (Fe,Mg) (sub 3) Si (sub 4) O (sub 10) (OH) (sub 2) ; talc-pyrophyllite group; in the banded iron formations of Minnesota. Syn: iron talc.

minor element

a. Trace element or accessory element. See also: trace element.

b. Less commonly, any of the elements present in the range of 0.1% to 1%, between major elements in concentrations greater than 1% and trace elements in concentrations less than 0.1%, or occasionally less than 0.01%.

minus sieve

In powder metallurgy, the portion of a powder sample that passes through a standard sieve of specified number. Contrast with plus sieve.

minus sight

See: foresight.

minus station

Stakes or points on the far side of the zero point from which a job was originally laid out.

minute of arc

A unit of angular measure equal to the 60th part of a degree and containing 60 s of arc.


An orthorhombic mineral, KAl (sub 2) (PO (sub 4) ) (sub 2) (OH,F).4H (sub 2) O ; in phosphate rock in Western Australia and South Australia.