Appendix:Dictionary of Mining, Mineral, and Related Terms/M/2

map
 * a. A horizontal projection of surface plants, mine workings, or both, drawn to a definite scale, upon which is shown all the important features of the mine; a plan; a plat.

b. The act of preparing such plans of a mine. c. A representation to a definite scale on a horizontal plane of the physical features of a portion of the Earth's surface (natural or artificial or both) by means of symbols, which may emphasize, generalize, or omit certain features as conditions may warrant. A map may be derived from ground surveys made by transit, plane table, or camera, or from aerial photographic surveys, or both.

map projection
 * A method of representing the curved surface of the Earth on a flat map. As the true shape of the Earth is a globe, it is impossible to make a map of large areas of the Earth's surface without some distortion.

marathon mill
 * A form of tube mill used in the cement industry, in which the pulverizing is done by long pieces of hardened steel shafting.

marbella
 * A Spanish magnetite with a siliceous gangue.

marble
 * a. A metamorphic rock composed essentially of calcite, dolomite, or a combination of the two, with a fine- to coarse-grained crystalline texture.

b. In commerce, any crystalline carbonate rock that will take a polish, including true marble, certain coarse-grained limestones, alabaster, and onyx. c. See: verde antique. CF: crystalline limestone.

marble handsaw
 * A toothless blade fitted at the back with a block handle, used with sand, for cutting slabs of marble into pieces.

marble saw
 * A toothless blade used with sand in marble cutting.

Marble's reagent
 * An etchant for stainless steels, consisting of 4 g of copper sulfate in 20 mL of hydrochloric acid and 20 mL of water.

marcasite
 * a. White iron pyrites, FeS (sub 2), the orthorhombic dimorph of pyrite, having a lower specific gravity, less stability, and a paler color. Often called white iron pyrites, coxcomb pyrites, and spear pyrites.

b. In the gemstone trade, marcasite is either pyrite, polished steel (widely used in ornamental jewelry in the form of small brilliants), or even white metal. c. An orthorhombic mineral, FeS (sub 2) ; dimorphous with pyrite; metallic; bronze-yellow to white; an authigenic or supergene mineral from acid solutions. Syn: white iron pyrites; white pyrite; cockscomb pyrite; spear pyrite; lamellar pyrite. d. The mineral group ferroselite, frohbergite, hastite, kullerudite, marcasite, and mattagamite. e. A gemstone with a metallic luster, esp. pyrite, but including polished steel and white metal. Syn: radiated pyrite.

marcus
 * A patented shaker screen with a nonharmonic or quick-return motion.

Marcy mill
 * A ball mill in which a vertical-grate diaphragm is placed near the discharge end. Between this perforated diaphragm and the end of the tube, there are arranged screens for sizing the material, oversize being returned for further grinding while undersize is discharged.

mare ball
 * York and Lanc. Spherical ferruginous concretions. CF: caballa ball.

marekanite
 * Obsidian that occurs as rounded to subangular bodies, usually less than 2 in (5.1 cm) in diameter and having indented surfaces. These bodies occur in masses of perlite and are of special interest because of their low water content as compared with the surrounding perlite. The name is from the Marekanka River, Okhotsk, Siberia, Russia.

margarite
 * a. A beadlike string of globulites, commonly found in glassy igneous rocks.

b. A monoclinic mineral, 4[CaAl (sub 2) (Al (sub 2) Si (sub 2) O (sub 10) )(OH) (sub 2) ] ; mica group; forms brittle folia; associated with corundum. Syn: brittle mica; pearl mica.

margarodite
 * A pearly variety of muscovite.

margarosanite
 * A triclinic mineral, Pb(Ca,Mn) (sub 2) Si (sub 3) O (sub 9).

marginal deposit
 * a. A magmatic segregation at the bottom and periphery of an intrusive rock; e.g., nickel-copper-sulfide deposits at Sudbury, ON, Canada.

b. Marginal ore deposit.

marginal fissure
 * A fracture, bordering an igneous intrusion, that has become filled with magma.

marginal ore deposit
 * A deposit near the lower limit of commercial workability.

marginal reserves
 * That part of the reserve base that, at the time of determination, borders on being economically producible. Its essential characteristic is economic uncertainty. Included are resources that would be producible, given postulated changes in economic or technologic factors.

marginal sea
 * An adjacent sea that is widely open to the ocean. See also: adjacent sea.

marginal thrust
 * A thrust fault along the margin of an intrusive that dips toward the intrusive.

marginal trench
 * See: trench.

maria glass
 * An early name for both mica and selenite (gypsum).

marialite
 * A tetragonal mineral, 3NaAlSi (sub 3) O (sub 8) .NaCl ; scapolite group; forms a series with meionite.

Marietta miner
 * Trade name for a heavy track-mounted continuous miner for operation in thick seams. The front end contains two cutter arms that rotate in opposite directions to sweep the coal it cuts inwards toward the center. The broken coal is taken back through the machine to a chain conveyor. Two cutter chains are arranged at roof and floor level behind the arms to cut down the coal left between the rotating arms. The machine cuts an area 12 ft (3.7 m) wide and 7 ft (2.1 m) high. Power is supplied by two motors, one of 70 hp (52.2 kW) and the other of 25 hp (17.4 kW). It has a continuous capacity from 3 to 3-1/2 st/min (2.7 to 3.2 t/min). This machine has been subject to several modifications. See also: continuous miner.

marine biology
 * Science that treats of the living organisms of the sea, the chemical and physical characteristics of their environment, and factors affecting their distribution.

marine core drill
 * Used for investigating strata beneath the seabed and taking sample and cores from which dredging conditions may be assessed.

marine deposit
 * A sedimentary deposit laid down in the sea, usually beyond the seaward edge of the littoral belt.

marine erosion
 * Erosion by moving seawater, the action of which is largely intensified by detritus carried by it.

marine geology
 * The marine science that treats of the topographical features of the sea bottom, the phenomena that have developed it, and the types, processes, and distribution of sedimentation.

marine humus
 * Organic matter deposited on the sea bottom.

marine invasion
 * The spreading of the sea over a land area.

marine mining
 * The mining of marine mineral deposits, classified as unconsolidated deposits such as gravel, mineral sands, or nodules; consolidated deposits such as outcrops, veins, or crusts; and fluid that is seawater or hydrothermal fluids; from, on, or beneath the seabed, whether on the continental shelf or in the deep ocean basins.

marine transgression
 * See: transgression.

mariposite
 * A chromian variety of phengite, a siliceous variety of muscovite.

maritime plants
 * Plants that grow naturally under salty conditions on a foreshore and that may materially help to prevent scour and stabilize sand dunes.

marker
 * a. An easily recognized stratigraphic feature having characteristics distinctive enough for it to serve as a reference or datum or to be traceable over long distances, esp. in the subsurface, as in well drilling or in a mine working; e.g., a stratigraphic unit readily identified, or any recognizable rock surface such as an unconformity or a corrosion surface. See also: format. Syn: marker bed; marker horizon; marker formation. CF: horizon.

b. A layer that yields characteristic reflections over a more or less extensive area. c. A layer that accounts for a characteristic segment of a seismic-refraction time-distance curve and can be followed over reasonably extensive areas. d. S. Afr. See: outcrop. e. See: marker block. CF: indicator.

marker bed
 * a. See: marker.

b. A stratigraphic bed selected for use in preparing structural, paleogeologic, and other maps that emphasize the nature or attitude of a plane or a surface. It is generally selected for lithologic characteristics, but biologic factors and unconformities may control. Syn: indicator; key bed; marker horizon. See also: horizon; marker. CF: indicator.

marker block
 * A small block on which the footage below the collar of a borehole is marked and inserted between pieces of core at its appropriate place in a core box to indicate the depth in the borehole at which the core was obtained. Also called footage block; footmark; marker. The marker block is placed in the core box on completion of each drilled interval. See also: marker.

marker formation
 * See: marker.

marker horizon
 * See: marker bed; marker.

market pot
 * In silver refining, the pot at the end of the series of pots used in the Pattinson process, in the direction in which the amount of silver left in the lead is diminishing. It contains the market lead.

markovnikovite
 * Variety of petroleum found in Russia.

marl
 * a. An old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay and calcium carbonate, formed under marine or esp. freshwater conditions; specif. an earthy substance containing 35% to 65% clay and 65% to 35% carbonate. Marl is usually gray; it is used esp. as a fertilizer for acid soils deficient in lime. In the Coastal Plain area of Southeastern United States, the term has been used for calcareous clays, silts, and sands, esp. those containing glauconite (greensand marls); and for newly formed deposits of shells mixed with clay.

b. A soft, grayish to white, earthy or powdery, usually impure, calcium carbonate precipitated on the bottoms of present-day freshwater lakes and ponds, largely through the chemical action of aquatic plants, or forming deposits that underlie marshes, swamps, and bogs that occupy the sites of former (glacial) lakes. The calcium carbonate may range from 90% to less than 30%. Syn: bog lime. c. A term occasionally used (as in Scotland) for a compact, impure, argillaceous limestone. Etymol: French marle.

marlite
 * See: marlstone.

marl slate
 * An English term for calcareous shale; it is not a true slate.

marlstone
 * a. An indurated rock of about the same composition as marl. It has a blocky subconchoidal fracture, and is less fissile than shale. Syn: marlite.

b. A term originally applied by Bradley (1931) to slightly magnesian calcareous mudstones or muddy limestones in the Green River Formation of the Uinta Basin, UT, but subsequently applied to associated rocks (including conventional shales, dolomites, and oil shales) whose lithologic characters are not readily determined. Picard (1953) recommended abandonment of the term as used in the Uinta Basin. c. See: marlstone ore.

marlstone ore
 * A stratified ironstone located in the Midlands (England) and occurring at the top of the Middle Lias series.

marly
 * Pertaining to, containing, or resembling marl; e.g., marly limestone containing 5% to 15% clay and 85% to 95% carbonate, or marly soil containing at least 15% calcium carbonate and no more than 75% clay (in addition to other constituents).

marmarization
 * See: marmorization.

marmarosh diamond
 * Rock crystal variety of quartz.

marmatite
 * A ferroan variety of sphalerite.

marmolite
 * A thinly foliated variety of serpentine.

marmorization
 * The conversion of limestone into marble by metamorphism. Syn: marmarization; marmorosis.

marmorosis
 * See: marmorization.

marm stone
 * Obsolete term for marble.

marokite
 * An orthorhombic mineral, CaMn (sub 2) O (sub 4) ; opaque black with dark red internal reflection; in Morocco.

Marriner process
 * A modification of the cyanide process in which the ore is deadroasted, after which all of it is ground to slime, and the resulting product is treated by agitation.

marrow
 * a. Well sinkers' term for a fine-grained floury rock, Oxfordshire, U.K.

b. Up to six workers who pool and share earnings equally, all at the same workplace but not necessarily on the same shift.

Marsaut lamp
 * An earlier type of miners' flame safety lamp fitted with two or three conical gauzes, thus adding to the safety of the lamp when used in high air velocities. The Marsaut lamp is the basis of modern flame safety lamps.

marsh buggy
 * A special, self-propelled geophysical vehicle designated to operate over marsh or extremely soft ground, usually having wheels with very wide tread or buoyant wheels that will float the vehicle in water.

Marsh funnel
 * An appliance for measuring viscosity. It consists of a copper funnel, about 30 cm long with a 15-cm diameter at the top, that has a 10-mesh screen over half its diameter to remove debris and a 6-mm-diameter exit tube at the bottom through which the rate of flow is timed. It takes 26 s for a quart of clean water to flow through and correspondingly longer for muds of greater viscosity. Gel strength is measured by comparing the rate of flow of freshly agitated mud with that of mud that has been allowed to remain quiescent for 10 min. See also: hydrometer; specific-gravity hydrometer.

marsh gas
 * a. Methane, CH (sub 4) . If the decaying matter at the bottom of a marsh or pond is stirred, bubbles of methane rise to the surface, thus the name marsh gas.

b. It is nonexplosive until met with air or oxygen. In miners' language synonymous with firedamp. See also: methane; firedamp.

marshite
 * An isometric mineral. CuI ; soft; oil brown; dodecahedral cleavage; at Broken Hill, New South Wales, Australia.

marsh ore
 * See: bog iron; bog iron ore.

marsh pan
 * A salt pan in a marsh.

martenite
 * A synthetic fettling material, used for sintering open-hearth furnace bottoms. The approximate composition (variable) is 5.2% silica, 2.1% alumina, 10.5% ferric oxide, 13.4% lime, 66.5% magnesia (ignition loss, 2.3%). Martenite sinters more rapidly than magnesite, thereby reducing repair time; moreover, it is suitable for hot patching. Martenite is as wear resistant as magnesite and has no deleterious effect on the slag.

martensite
 * Alpha-iron supersaturated with carbon as a result of quenching austinite (gamma-iron) below 150 degrees C. (Not martinsite.)

martic
 * A mixture of bituminous matter, such as asphalt, and some foreign material, such as sand.

Martin process
 * Used in the manufacture of steel. Also called Siemens-Martin and open-hearth process.

martinsite
 * See: kieserite. (Not martensite.)

martite
 * Hematite pseudomorphous after magnetite octahedra.

martourite
 * See: berthierine.

marundite
 * A coarse-grained pegmatite consisting of corundum and margerite with accessory biotite, plagioclase, apatite, tourmaline, garnet, and kyanite. Allied to plumasite grading into normal pegmatite.

mascagnite
 * An orthorhombic mineral, (NH (sub 4) ) (sub 2) SO (sub 4) ; occurs around fumaroles and in guano deposits.

mascot emerald
 * A beryl triplet that simulates emerald.

maser
 * Contracted version of microwave amplification by simulated emission of radiation. A class of amplifier from which the optical laser was developed. See also: laser.

mask
 * a. A screen, usually made of tracing cloth, to subdue and diffuse the light behind a plumbline or other sighted object.

b. See: respirator.

maskeeg
 * See: muskeg.

maskelynite
 * A plagioclase glass in some chondrites and irons formed by preterrestrial impact between meteorites in space.

mason's hammer
 * A square-faced hammer with a peen in line with handle.

mass
 * a. The quantity of matter in a body, obtained by dividing the weight of the body by the acceleration due to gravity.

b. A large irregular deposit of ore, which cannot be recognized as a vein or bed. See also: nontabular deposit.

mass aqua
 * Borosilicate glass imitative of aquamarine (beryl).

mass copper
 * In the Lake Superior region, a term for native copper occurring in large masses.

mass density
 * Mass of air per unit volume. Measured in kilograms per cubic meter.

mass detonation
 * A term applied to the unintentional detonation of all or a part of a large quantity of explosive material (bulk truckload, shipload, or caseload) by the explosion of a smaller quantity of explosives or a flame.

mass diagram
 * A plotting of cumulative cuts and fills used for engineering computation of highway jobs.

mass effect
 * The tendency for hardened steel to decrease in hardness from the surface to the center, as a result of the variation in the rate of cooling throughout the section. Becomes less marked as the rate of cooling required for hardening decreases; i.e., as the content of alloying elements increases.

mass fiber
 * a. One of the three recognized forms in which asbestos fiber is found in rock deposits. In this form the fibers are usually found intermixed in a matrix, which forms the orebody. Found mostly in the matrix of the deposits of the amphibole varieties of asbestos. The rock forming the orebody is sometimes inclined to be soft, and the fibers intermingled in such a mass deposit consist of patches of apparent slip-fiber forms. Indications of disturbed cross-fiber disposition are often discernible.

b. A mass aggregate of interlaced, unoriented, or radiating fibers of chrysotile serpentine asbestos.

mass haul diagram
 * Diagram used in construction work to show the location of digging and filling sites, and the distances over which earth and materials are to be transported.

massicot
 * An orthorhombic mineral, PbO ; dimorphous with litharge; prismatic cleavage; soft; yellow; occurs in oxidized zones of lead ore deposits. Syn: lead ocher.

massif
 * A massive topographic and structural feature, esp. in an orogenic belt, commonly formed of rocks more rigid than those of its surroundings. These rocks may be protruding bodies of basement rocks or younger plutonic bodies. Examples are the crystalline massifs of the Helvetic Alps, whose rocks were deformed mainly during the Hercynian orogeny, long before the Alpine orogeny.

massifs long
 * Fr. Pillar in longwall workings.

massive
 * a. Said of a mineral deposit (esp. of sulfides) characterized by a great concentration of ore in one place, as opposed to a disseminated or vein deposit.

b. Said of any rock that has a homogeneous texture or fabric over a wide area, with an absence of layering, foliation, cleavage, or any similar directional structure. See also: massive rock. c. Said of a mineral that is physically isotropic; i.e., lacking a platy, fibrous, or other structure. CF: amorphous.

massive bedding
 * Very thick homogeneous stratification in sedimentary rocks.

massive eruption
 * Outpouring of lava from a line or system of fissures, so that vast areas have become covered by nearly horizontal sheets of extrusive flows.

massive mineral
 * If the crystalline grains are so small that they cannot be distinguished except under the high magnification of a microscope, the structure is described as compact and the mineral as massive.

massive pluton
 * Any pluton that is not tabular in shape.

massive rock
 * Isotropic, homogeneous rock with a strength that does not vary appreciably from point to point. Typical examples are igneous rocks such as granite and diorite; metamorphic rocks such as marble and quartzite; and some thick-bedded sedimentary rocks. See also: massive.

mass movement
 * The unit movement of a portion of the land surface; specif. the gravitative transfer of material down a slope. Syn: mass-wasting.

mass number
 * The sum of the neutrons and protons in a nucleus. It is the nearest whole number to the actual atomic weight of the atom.

mass profile
 * A road profile showing cut and fill in cubic yards or meters.

mass shooting
 * Simultaneous exploding of charges in all of a large number of holes, as contrasted with sequential firing with delay caps.

mass spectra
 * Positive ray spectra obtained by means of a mass spectrograph. In such spectra the images due to positive ray particles of different masses are spaced according to the masses of the particles; i.e., according to their atomic weights.

mass spectrometer
 * An instrument for producing and measuring, usually by electrical means, a mass spectrum. It is esp. useful for determining molecular weights and relative abundances of isotopes within a compound.

mass unit weight
 * See: wet unit weight.

mass-wasting
 * See: mass movement.

mast
 * to its operating position by mechanical means.

b. A single pole, used as a drill derrick, supported in an upright or operating position by guys. c. A tower or vertical beam carrying one or more load lines at its top.

master alloy
 * An alloy, rich in one or more desired addition elements, that can be added to a melt to raise the percentage of a desired constituent.

master hauler
 * S. Wales. The person in charge of haulers in a coal mine and who controls the horse haulage traffic and the allocation of trams.

master joint
 * A persistent joint plane of greater-than-average extent.

master lode
 * The main productive lode of a district. CF: mother lode.

master pin
 * The only pin in an integrated crawler track that will open the track when driven out.

mastershifter
 * N. of Eng. Official responsible for the working of a seam during the third (night) shift of the day.

master station
 * A position in the ventilation circuit of a mine specially chosen for the regular and accurate estimation of the total quantity of air circulating.

mat
 * a. An accumulation of broken mine timbers, rock, earth, etc., coincident with the caving system of mining. As the ore is extracted, the mat gradually settles and forms the roof of the working levels, slopes, etc.

b. Lusterless or dull surface in a metal, produced by a method of finishing.

match
 * The part of a detonator that is most easily ignited.

materials flowsheet
 * A flowsheet principally concerned with solid materials. See also: operational capacities.

materials handling
 * The art and science involving movement, packaging, and storage of substances in any form.

materials lock
 * An air lock through which materials are passed into or out of a pneumatic caisson or a shaft being driven under air pressure. See also: manlock.

Mathewson's device
 * An apparatus for separating matte and slag at lead-silver blast furnaces where matte is of secondary importance.

matildite
 * A hexagonal mineral, AgBiS (sub 2) ; forms prismatic crystals; sp gr, 6.9 (super ) . Syn: schapbachite; plenargyrite.

matlockite
 * A tetragonal mineral, 2[PbFCl] ; basal cleavage; an alteration of galena or lead-bearing slags.

mat pack
 * Small pack of timber consisting of a number of timbers laid side by side to form a solid mass 2 to 2-1/2 ft square by 4 to 6 in thick (approx. 0.7 m square by 10 to 15 cm thick). Holes are drilled edgeways through the mat, and wires are threaded through to hold it together. Mats are transported underground and built up to form very effective supports.

matraite
 * A trigonal mineral, ZnS ; trimorphous with sphalerite and wurtzite.

matrix
 * a. The nonvaluable minerals in an ore; the gangue.

b. The rock material in which a fossil, crystal, or mineral is embedded. Syn: groundmass. c. A local term for the phosphate-bearing gravel in the land-pebble deposits of Florida. d. The metal in which the diamonds inset in the crown of a bit are embedded. e. The material that forms a cushion or binder in the construction of pavement. f. The finer-grained material between the larger particles of a rock or the material surrounding a fossil or mineral. g. The principal phase or aggregate in which another constituent is embedded. h. In electroforming, a form used as a cathode.

matrix metal
 * The continuous phase of a polyphase alloy or mechanical mixture; the physically continuous metallic constituent in which separate particles of another constituent are embedded.

matrosite
 * A microscopical constituent of torbanite; opaque, black mass forming its groundmass. CF: gelosite; humosite; retinosite.

matte
 * A metallic sulfide mixture made by melting the roasted product in smelting sulfide ores of copper, lead, and nickel.

matte fall
 * Weight of matte expressed as a percentage of the total charge.

matte smelting
 * The smelting of copper-bearing materials, usually in a reverberatory furnace. The valuable product is a liquid, copper-iron sulfide called matte.

matting
 * The process of smelting sulfide ores into matte.

mattock
 * a. A miner's pickax.

b. An implement that combines the features of an adz, ax, and pick, and is used for digging, grubbing, and chopping.

Matura diamond
 * Colorless to faintly smoky gem-quality zircon from the Matara (Matura) district of Sri Lanka; any smokiness is removable by heating.

mature
 * a. Pertaining to the stage of maturity of the cycle of erosion; esp. said of a topography or region having undergone maximum development and accentuation of form; or of a stream (and its valley) with a fully developed profile of equilibrium; or of a coast that is relatively stable.

b. Said of a clastic sediment that (1) has been differentiated or evolved from its parent rock by processes acting over a long time and with a high intensity and (2) is characterized by stable minerals (such as quartz), deficiency of the more mobile oxides (such as soda), absence of weatherable material (such as clay), and well-sorted but subangular to angular grains. Example: a clay-free mature sandstone on a beach.

maturity
 * a. A stage in the development of a coast that is characterized by straightening of the shoreline by bridging of bays and cutting back of headlands so as to produce a smooth, regular shoreline consisting of sweeping curves; and, eventually, retrogradation of the shore beyond the bayheads so that it lies against the mainland as a line of eroded cliffs throughout its course.

b. The extent to which a clastic sediment texturally and compositionally approaches the ultimate end product to which it is driven by the formative processes that operate upon it. c. The stage in the development of a stream at which it has reached its maximum efficiency, having attained a profile of equilibrium and a velocity that is just sufficient to carry the sediment delivered to it by tributaries. d. The second of the three principal stages of the cycle of erosion in the topographic development of a landscape or region, intermediate between youth and old age (or following adolescence), lasting through the period of greatest diversity of form or maximum topographic differentiation, during which nearly all the gradation resulting from operation of existing agents has been accomplished.

maturity index
 * A measure of the progress of a clastic sediment in the direction of chemical or mineralogic stability; e.g., a high ratio of alumina-soda, of quartz-feldspar, or of quartz + chert-feldspar + rock fragments indicates a highly mature sediment.

maucherite
 * A tetragonal mineral, Ni (sub 11) As (sub 8) ; forms tabular crystals; occurs in nickel-cobalt-native-silver ore deposits. Syn: placodine; temiskamite.

Mawco cutter loader
 * A cutter loader similar to an Anderton shearer except that the drum is replaced by a frame jib 42 in (107 cm) high and 20 in (51 cm) deep. The machine travels on an armored flexible conveyor at a speed of about 4-1/2 ft/min (1.4 m/min). It cuts a 20-in (51-cm) web on the cutting run, and the plow deflector loads the cut coal onto the conveyor. On the reverse run, the deflector loads all the loose coal left on the track, and the conveyor is snaked over behind the machine. The loader is suitable for medium-thickness seams, and the yield of large coal is good.

maximum and minimum densities
 * In soil tests, the maximum density is found by compacting soil with a Kango hammer; the minimum density is measured by pouring soil into a container of known capacity. This test is useful for determining the relative density of sands, by comparison with field tests.

maximum angle of inclination
 * The maximum angle at which a conveyor may be inclined and still deliver a predetermined quantity of bulk material within a given time. As the maximum angle is approached, the rate of handling of bulk material is usually decreased.

maximum belt slope
 * The slope beyond which the material on a conveyor tends to roll downhill. The maximum slope on which a conveyor can operate depends on (1) the material carried, (2) the loading or feeding efficiency, (3) the size and type of belt, and (4) the environment. In general, in the case of run-of-mine coal and ore, belt conveyors can operate up to about 18 degrees . If the material conveyed contains large lumps, spillage may result if the belt is too narrow.

maximum belt tension
 * The total of the starting and operating tensions. In the average conveyor this is considered to be the same as the tight side tension.

maximum carbon dioxide content
 * The recommended maximum allowable concentration of carbon dioxide in mine air is 0.5%.

maximum charge weight per delay
 * The maximum quantity of explosive charge detonated on one interval (delay) within a blast. The charge detonated within any 8-ms interval over the entire duration of the blast.

maximum demand
 * Upper limit of electric power that may be drawn at any time from the mains without penalty, as agreed by contract.

maximum density
 * See: maximum unit weight.

maximum dry density
 * The dry density obtained by the compaction of soil at its optimum moisture content.

maximum microcline
 * Microcline with the most complete ordering possible of aluminum and silicon ions in the tetrahedral sites and the smallest angle for beta (maximum triclinicity). CF: mesomicrocline.

maximum operating belt tension
 * The tension in the carrying run necessary to maintain the normal operating speed of a loaded belt.

maximum per delay
 * The maximum vibration at distant points is that which has been generated by the greatest amount of explosive fired at any one instant.

maximum-pressure arch
 * See: pressure arch theory.

maximum-pressure gage
 * An instrument for registering the maximum pressure occurring during an explosion at the point where the instrument is located.

maximum subsidence
 * The maximum amount of subsidence in a subsidence basin. The value of maximum subsidence for a given seam thickness depends on the underground geometry and the thickness and character of the overburden. See also: subsidence factor.

maximum unit weight
 * The dry unit weight defined by the peak of a compaction curve. Syn: maximum density. See also: unit weight.

Maxton screen
 * A screening machine of the trommel class, rotating on rollers that support the tube. There are radial elevating ribs to prevent wear of screen cloth and to elevate the oversize. Unscreened material is delivered on the inside screen surface, undersize passes through, and oversize is elevated and discharged into a separate launder.

maxwell
 * The cgs (centimeter-gram-second) unit of magnetic flux. One maxwell = 10 (super -8) Wb, or the flux through 1 cm (super 2) normal to a field of magnetic induction of 1 Gs.

Maxwell's rule
 * A law stating that every part of an electric circuit is acted upon by a force tending to move it in such a direction as to enclose the maximum amount of magnetic flux.

Mayari iron
 * Pig iron made from Cuban ores that contain vanadium and titanium, or pig iron made to duplicate the Cuban iron.

mayenite
 * An isometric mineral, Ca (sub 12) Al (sub 14) O (sub 33) ; occurs in metamorphosed marly limestone; an important constituent of portland cement clinker.

mboziite
 * A potassian variety of taramite amphibole.

McGinty
 * Three sheaves over which a rope is passed so as to take a course somewhat like that of the letter M. The resulting friction causes the rope to slide with difficulty. It is used for lowering loaded cars from the face to the mouth of a room on a steep roadway.

mcgovernite
 * A trigonal mineral, (Mn,Mg,Zn) (sub 22) (AsO (sub 3) )(AsO (sub 4) ) (sub 3) (SiO (sub 4) ) (sub 3) (OH) (sub 20) ; reddish-bronze; forms granular masses with perfect basal cleavage. Also spelled macgovernite.

McKelvey diagram
 * A graphical classification of mineral resources according to economic viability and certainty of existence. Used by the U.S. Bureau of Mines and the U.S. Geological Survey in their definitions of mineral resources and reserves, USGS Circular 831. Named after Vincent E. McKelvey, ninth director of the U.S. Geological Survey.

McLuckie gas detector
 * This nonautomatic detector, or portable air analysis apparatus, can be used underground, or samples of air can be brought out of the mine in small rubber bladders and analyzed at the surface. This apparatus depends for its action on the fact that when methane is burned in air (oxygen) a definite chemical action takes place. When the resulting steam condenses to water there is a reduction in pressure and in the McLuckie detector this reduction of pressure, which is proportionate to the methane present, is indicated by the height of the liquid in one limb of the U-tube which rises up the side of the scale: the scale is graduated from 0% to 3% in steps of 0.1%.

McNally-Carpenter centrifuge
 * A fine-coal dewatering machine consisting of a conical rotating element with a vertical axis, built up of three rows of perforated stainless steel screen plates or stainless steel wedge or round-wire sections cut and rolled to conform to the surface of the cone. Wet feed is deposited by gravity into the top of the cone-shaped dryer onto a distributing disk that throws the material by centrifugal force onto the stepped screen or basket. The rapid circular movement of the basket forces the water through the screen, while the coal moves toward the bottom. Peripheral velocity and centrifugal force become greater for each particle, breaking down the surface tension of water film on each piece, increasing drying action directly in ratio to the cone circumference and peripheral speed. The most effective drying area is at the bottom of the cone just before the material is discharged from the machine. See also: dewatering.

McNally-Norton jig
 * In this jig, raw coal is conveyed to a wash box through sluices. Air pulsations are transmitted through valves to water in a compartment adjacent to the washing bed, causing the water in the wash box to rise. Pulsating water causes the incoming fuel to be loosely suspended in the water and permits heavier refuse to sink to the screen plate while suspended coal spills over into the second compartment. In the second compartment the process is repeated with the remaining refuse sinking to the screen and clean coal discharging to the dewatering screens.

McNally-Vissac dryer
 * A convection dryer of the forced-draft type. The heat source is a coal-fired furnace. It consists essentially of a declined reciprocating screen over which the coal travels. Two balanced tandem decks are used. They are suspended from the supporting structure by inclined flexible hangers and actuated in opposition through flexible pitmans from a common eccentric shaft. The removal of moisture is accomplished by passing hot furnace gases, tempered with cold air, downward through the bed of coal as it travels along the screen. An induced-draft fan at the exhaust end provides the motive force for the gases. See also: thermal drying.

McNamara clamp
 * A drill-rod safety clamp somewhat similar to a Wommer's safety clamp.

M-design core barrel
 * Standard-design, double-tube, swivel-type core barrel made in sizes to be used with appropriate standard ranges of diamond-drill fittings. Its distinguishing features are that a 2-1/2 degrees taper core lifter is carried inside a short tubular sleeve (called a lifter case) coupled to the bottom end of the inner tube, and that the lifter case extends downward inside the bit shank to within a very short distance behind the face of the core bit.

M-discontinuity
 * See: Mohorovicic discontinuity.

M.E. 6 exploder
 * An exploder approved for firing six shots simultaneously in British coal mines. It contains a 67-1/2-V high-tension dry battery, used to charge a 150-mu F condenser, which in turn is discharged through the shotfiring circuit by a firing key. The test circuit and an ohmmeter are incorporated in the exploder, thc ohmmeter pointer moving over a scale to indicate whether or not the external circuit is in order. A pushbutton disconnects the test circuit from the external circuit and makes connection with the firing circuit. See also: blasting machine.

meadow ore
 * See: bog iron; bog iron ore; limonite.

meager feel
 * Moistureless; dry and rough to the touch, such as chalk and magnesite.

mean
 * An arithmetic average of a series of values; esp. arithmetic mean. CF: mode.

mean birefringence
 * The numeral that represents the average between the greatest strength of double refraction and the least strength of double refraction possessed by a species or variety. The refractive index of sphene, e.g., is 1.885 to 1.990 and 1.915 to 2.050; hence the birefringence ranges from 0.105 to 0.135. The average, or mean, is 0.120. Syn: refractive index.

mean calorie
 * One-hundredth of the heat required to raise 1 g of water from 0 degrees C to 100 degrees C.

mean depth
 * The cross-sectional area of a stream divided by its width at the surface.

meander
 * a. One of a series of regular, freely developing sinuous curves, bends, or loops in the course of a stream. It is produced by a mature stream swinging from side to side as it flows across its floodplain or shifts its course laterally toward the convex side of an original curve. Etymol: Greek maiandros, from Maiandros River in western Asia Minor (now known as Menderes River in SW Turkey), proverbial for its windings.

b. To wind or turn in a sinuous or intricate course; to form a meander.

meander belt
 * That part of a floodplain between two lines tangent to the outer bends of all the meanders. It is the zone within which channel migration occurs, as indicated by abandoned channels, accretion topography, and oxbow lakes.

meander line
 * A line run in a survey of a mining claim bordering on a stream or other body of water, not as a boundary of the tract surveyed, but for the purpose of defining the sinuosities of the bank or shore of the water, and as a means of ascertaining the quantity of land within the surveyed area.

mean effective pressure
 * In an air compressor, the equivalent average pressure exerted by the piston throughout a stroke.

mean radiant temperature (mrt)
 * Single temperature of all enclosing surfaces that would result in the same heat emission as the same surface with various different temperatures.

mean refractive index
 * a. The index of refraction measured for the D line of sodium.

b. For uniaxial crystals: (2n (sub omega ) +n (sub epsilon ) )/3. For biaxial crystals: (n (sub alpha ) +n (sub beta ) +n (sub gamma ) )/3.

mean size
 * The weighted average particle size of any sample, batch, or consignment of particulate material.

mean sphere depth
 * The uniform depth to which water would cover the Earth if the solid surface were smoothed off and parallel to the surface of the geoid. Generally accepted as a depth of 2,440 m.

mean stress
 * a. In fatigue testing, the algebraic mean of the maximum and minimum stress in one cycle. Also called the steady-stress component.

b. In any multiaxial stress system, the algebraic mean of three principal stresses; more correctly called mean normal stress.

measured depth
 * See: measured drilling depth.

measured drilling depth
 * The apparent depth of a borehole as measured along the longitudinal axis of the borehole. The measured drilling depth is always equal to the unoverlapped drilled footage in a borehole. Also called measured depth. Sometimes abbreviated md.

measured resources
 * Resources from which the quantity is computed from dimensions revealed in outcrops, trenches, workings, or drill holes; grade and/or quality are computed from the results of detailed sampling. The sites for inspection, sampling, and measurement are spaced so closely and the geologic character is so well defined that size, shape, depth, and mineral content of the resource are well established. See also: reserves.

measurement
 * The finding of the number of units of measure in a line, area, space or volume, period of time, etc.

measurement of concentration
 * Gr. Brit. At the National Coal Board collieries, in order to assess the degree of concentration, certain basic data are collected, involving the pithead output, length of main haulage roads, and length of coalface in production. See also: face concentration; geographical concentration; overall concentration.

measures
 * A group or series of sedimentary rocks having some characteristic in common; specif. coal measures. The term apparently refers to the old practice of designating the different seams of a coalfield by its measure or thickness.

measures head
 * A heading or drift made in various strata.

measuring chain
 * A surveyor's chain, containing 100 links of 7.92 in (20.12 cm) each.

measuring chute
 * A bin installed adjacent to the shaft bottom in skip winding. The capacity of the chute is equal to that of the skip used, ranging from 4 to 10 st (3.6 to 9.1 t). Bin-feeding arrangements differ but may be by a steelplate conveyor from a surge bunker that in turn receives the ore or coal from the mine cars or a trunk conveyor. A measuring chute ensures a quick and correct loading of skips without spillage. Immediately the skip is positioned in line, the measuring chute bottom door opens and material is discharged into the skip. See also: pocket. Syn: underground ore bin.

measuring day
 * The day when face or other work is measured and recorded for assessing wages.

measuring element
 * In flotation, that portion of the feedback elements that converts the signal from the primary detecting element to a form compatible with the reference input.

measuring pocket
 * Storage space near an entry from underground workings to a hoisting shaft; laid out so as to deliver a measured volume into a hoisting skip and to be refilled before the skip returns empty.

measuring tape
 * A graduated tape, steel or linen, usually in 50-ft or 100-ft (15-m or 30.4-m) lengths; used by engineers, builders, surveyors, etc.

measuring weir
 * A device for measuring the flow of water. It generally consists of a rectangular, trapezoidal, triangular, or other shaped notch in a thin plate in a vertical plane through which the water flows. The weir head is an index of the rate of flow. See also: notch.

mechanical advantage
 * Ratio between the resistance or load raised by a machine, and the applied force. Mechanical advantage divided by velocity ratio gives the efficiency of the machine.

mechanical air machine
 * A flotation machine that utilizes pulp-body concentration by the agitation froth method and bubble-column action by pneumatic and cascade means.

mechanical analysis
 * Determination of the particle-size distribution of a soil, sediment, or rock by screening, sieving, or other means of mechanical separation; the quantitative expression of the size-frequency distribution of particles in granular, fragmental, or powdered material. It is usually expressed in percentage by weight (and sometimes by number or count) of particles within specific size limits. See also: particle-size analysis.

mechanical classifier
 * One of the machines, such as the Dorr classifier, that are commonly used to classify a ball-mill or rod-mill discharge into finished product and oversize.

mechanical clay
 * A clay formed from the products of the abrasion of rocks.

mechanical cleaning
 * The removal of impurities by mechanical units as compared with hand picking. Broadly, mechanical cleaning may be subdivided into dry cleaning and wet cleaning.

mechanical efficiency
 * The ratio of the air-indicated horsepower to the indicated horsepower in a power cylinder, in the case of compression driven by steam or internal-combustion engines, and to the brake horsepower delivered to the shaft in the case of a power-driven machine.

mechanical equivalent of heat
 * Amount of mechanical energy that can be transformed into a single heat unit; the equivalent of 778 ft.lbf/Btu (1,000 N.m/kJ).

mechanical extensometer
 * An appliance for measuring strain; often used in roof control investigations. It employs a micrometer dial gage actuated through a lever giving initial magnification of the movement. See also: acoustic-strain gage; electrical resistance strain gage.

mechanical loader
 * A cell in which the solids-water pulp feed is kept agitated, and is circulated by means of an impeller mounted at the bottom of a vertical shaft. The rotating impeller creates vacuum enough to draw air down the standpipe surrounding the impeller shaft, and the impeller disperses the air throughout the pulp in the form of small bubbles. The flotable minerals are carried upward by the bubbles and eventually collect in the froth above the pulp in the machine. Automatic scrapers remove the mineral-laden froth that contains the concentrate, and after the values have been removed, the barren pulp containing the tailing flows out of the cell. /;   �N ��N ��� �       � e DICTIONARY TERMS:mechanical loader A power machine for loading mater A power machine for loading material. See also: loader.

mechanical mixture
 * A composition of two or more substances, each remaining distinct, and generally capable of separation by mechanical means.

mechanical properties
 * Of metals: the elastic limit, elongation, fatigue range, hardness, maximum stress, reduction in area, shock resistance, and yield point.

mechanical puddler
 * A wrought-iron (rocking) furnace in which puddling is done by mechanical motion instead of by hand.

mechanical puddling
 * See: mechanical puddler.

mechanical rabble
 * A rabble worked by machinery. See also: rabble.

mechanical rammer
 * A machine embodying a weight that is lifted and dropped upon the material being rammed. See also: power rammer.

mechanical sampling
 * Mechanical sampling systematically removes a portion of the stream of material for a sample. Mechanical sampling is widely used in cone preparation plants and concentrators where large quantities of materials are to be sampled, while hand sampling is used for smaller amounts. CF: hand sampling.

mechanical sediment
 * Sediment that has been brought to its places of deposition as separate particles by mechanical means. Water, wind, and ice are the agents commonly involved; the resulting rocks are conglomerate, sandstone, siltstone, shale, and certain limestones.

mechanical set
 * Bits produced by the various means in which diamonds are set in a bit mold into which a cast or powder metal is placed, embedding the diamonds and forming the bit crown, as opposed to handsetting. Also, the act or process of producing diamond bits in such a manner. Also called cast set; machine set; sinter set. CF: handset.

mechanical-set bit
 * A diamond bit produced by mechanical methods as opposed to handsetting methods. See also: mechanical set.

mechanical shovel
 * A loader limited to level or only slightly graded drivages. The machine operates a shovel in front of it and pushes itself forward; when full, the shovel is swung over the machine and delivers into a mine car or tub behind. It will shunt, pull, and push its own cars, delivering them into a shunt or passby when full. See also: shovel loader.

mechanical stabilization
 * Mixing two or more poorly graded soils to obtain a well-graded one.

mechanical weathering
 * The process of weathering by which frost action, salt-crystal growth, absorption of water, and other physical processes break down a rock to fragments, involving no chemical change. CF: chemical weathering. Syn: disintegration.

mechanical working
 * Subjecting metal to pressure exerted by rolls, presses, or hammers, to change its form or affect the structure, and therefore the physical properties.

mechanical yielding prop
 * A steel prop in which yield is controlled by friction between two sliding surfaces or telescopic tubes. Although crude when compared with the hydraulic prop, the friction yield prop is very robust, is cheap, and requires little maintenance.

mechanics
 * The branch of physics that treats of the phenomena caused by the action of forces on material bodies. It is subdivided into statics, dynamics, or kinetics; or into the mechanics of rigid bodies and hydromechanics (including hydrostatics and hydrodynamics).

mechanization
 * Essentially, the introduction of power machines to replace manual labor. In coal mining, it may denote the introduction of conventional machine mining to replace hand mining, or continuous mining to replace conventional machine mining.

mechanization engineer
 * Usually a qualified mining engineer with first-hand experience and knowledge of the various mining machines and the physical conditions most suitable for them. In general, the National Coal Board, Great Britain, appoints a mechanization engineer for each group of collieries.

mechanization scheme
 * A plan or project to convert a handmining or a conventional machine mining face to mechanized mining; i.e., the use of machines that either load prepared coal or cut and load coal simultaneously (cutter loaders). The scheme may also include the introduction of locomotives, skip winding, etc.

mechanized
 * Term descriptive of a mine that has a high percentage of machinery for all steps of mining and handling mineral product, from the face to the mine working place, and on to the tipple or treatment plant.

mechanized heading development
 * A pillar method of working suitable for seams 4 ft (1.2 m) and over in thickness. Three or more narrow headings are driven rapidly with machines at about 30-yd (10-m) centers with crosscuts for ventilation. The headings are 10 ft (3 m) or more wide and 5 to 6 ft (approx. 2 m) high or seam thickness. Upon reaching the boundary, the pillars formed by the headings are extracted, again with machines, on the retreat. This method is favored in the United States and the heading work is quite as productive, if not more so, than pillar working. See also: entry; longwall retreating.

mechanized output
 * The coal produced by all coal face machinery that either loads prepared coal or cuts and loads coal simultaneously. Also includes all coal obtained by hand filling on faces where an armored flexible conveyor is used on a prop-free front.

Meco-Moore cutter loader
 * A heavy 120-hp (89.5-kW) cutter loader. The first Meco-Moore was used in a Lancashire, England, colliery in 1934. See also: A.B. Meco-Moore.

medfordite
 * See: moss agate.

median diameter
 * An expression of the average particle size of a sediment or rock, obtained graphically by locating the diameter associated with the midpoint of the particle-size distribution; the middlemost diameter that is larger than 50% of the diameters in the distribution and smaller than the other 50%.

medical lock
 * An air chamber comprising steel cylinder 18 ft (5.5 m) long and about 6 ft (1.8 m) in diameter, which has airtight doors at one end and is closed at the other. It is used for immediate treatment of sufferers from caisson disease.

Medina emerald
 * Green glass emerald simulant.

mediosilicic
 * A term proposed by Clarke (1908) to replace intermediate. CF: subsilicic; persilicic. See also: intermediate.

Mediterranean suite
 * A major group of igneous rocks, characterized by high potassium content. This suite was so named because of the predominance of potassium-rich lavas around the Mediterranean Sea; specif. those of Vesuvius and Stromboli. CF: Atlantic suite; Pacific suite.

medium
 * Any suspension of medium solids in water.

medium band
 * A field term that, in accordance with an arbitrary scale established for use in describing banded coal, denotes a vitrain band ranging in thickness from approx. 1/12 to 1/5 in (2 to 5 mm).

medium draining screen
 * A screen for draining the separating medium from dense-medium bath products.

medium-grained
 * a. Said of an igneous rock, and of its texture, in which the individual crystals have an average diameter in the range of 0.04 to 0.2 in (1 to 5 mm).

b. Said of a sediment or sedimentary rock, and of its texture, in which the individual particles have an average diameter in the range of 1/16 to 2 mm (62 to 2,000 mu m, or sand size). CF: coarse-grained; fine-grained.

medium-inclined
 * Said of deposits and coal seams with a dip of 25 degrees to 40 degrees.

medium pressure
 * When applied to valves and fittings, means suitable for a working pressure of 125 to 175 psi (860 to 1,200 kPa).

medium-recovery screen
 * A composite screen for draining and spraying the product from a dense-medium bath to remove adherent medium solids.

medium-round nose
 * A diamond bit the cross-sectional outline of which is partially rounded but not as fully rounded as a double-round nose bit. Syn: half-round nose; modified-round nose.

medium solids
 * The solid component of a dense-medium suspension.

medium-solids preparation
 * Any purification or grinding of the raw dense-medium solids to make them suitable for use.

medium-solids recovery
 * See: dense-medium recovery.

medium-solids recovery plant
 * The equipment used to remove adherent medium solids from a product from a dense-medium bath (after drainage of surplus medium), usually by spraying, and to remove contaminating coal and clay from these medium solids.

medium-stone bit
 * A bit with diamonds ranging from 8 to 40 per carat in size.

medium-thickness seam
 * In general, a coal seam over 2 ft (0.6 m) and up to 4 ft (1.2 m) in thickness.

medium-volatile bituminous coal
 * The rank of coal, within the bituminous class of Classification D 388, such that, on the dry and mineral-matter-free basis, the volatile matter content of the coal is greater than 22% but equal to or less than 31% (or the fixed carbon content is equal to or greater than 69% but less than 78%), and the coal commonly agglomerates. CF: bituminous coal.

medium voltage
 * In coal mining, voltage from 661 to 1,000 V. CF: high voltage; low voltage.

medmontite
 * A mixture of chrysocolla and mica. See also: cupromontmorillonite.

meehanite
 * High-duty cast iron produced by ladle addition of calcium silicide.

meerschaum
 * See: sepiolite.

meet
 * a. Eng. To keep pace with; e.g., to keep sufficient supply of coal at the pit bottom to supply the winding engine.

b. To come together exactly, as in survey lines from opposite directions.

meeting
 * a. A siding or bypass on underground roads.

b. Newc. The place at middle-depth of a shaft, slope, or plane, where ascending and descending cars pass each other.

meeting post
 * A vertical timber at the outer edge of each of a pair of lock gates, mitered so that the gates fit tightly when closed.

mega-
 * a. A prefix meaning large. As a prefix to petrological and other geologic terms, it signifies parts or properties that are recognizable by the unaided eye. Opposite of micro-.

b. A combining form meaning 1 million times; e.g., megavolt for 1 million volts.

megabar
 * A unit of pressure equal to 1 Mdyn/cm (super 2).

megacycle
 * A unit of 1 million cycles.

megaphenocryst
 * A phenocryst that is visible to the unaided eye.

megascopic
 * Said of an object or phenomenon, or of its characteristics, that can be observed with the unaided eye or with a hand lens. Syn: macroscopic. CF: microscopic.

megaseismic region
 * The most disturbed earthquake area.

megaspore
 * Female spore; part of the reproduction organs of many coal measures plants. See also: spore.

Megator
 * A displacement type of pump operating on the eccentric principle.

megger
 * An electrical measuring instrument comprising a hand-operated generator equipped with a governor, a moving measuring system consisting of a voltage, and a current coil so disposed that the deflection of the moving system is proportional to the ratio of voltage to current. Used to measure insulation resistance and resistance to ground. It has been used to some extent in electrical prospecting.

Meigen's reaction
 * A test to distinguish calcite from aragonite. After boiling for 20 min in a cobalt nitrate solution, aragonite becomes lilac, the color showing in thin section, while calcite and dolomite become pale blue, the color not showing in thin section.

meionite
 * A tetragonal mineral, 3CaAl (sub 2) Si (sub 2) O (sub 8) .CaCO (sub 3) ; scapolite group; forms a series with marialite.

meizoseismal
 * Of or pertaining to the maximum destructive force of an earthquake.

meizoseismal area
 * The most disturbed area within the innermost isoseismal line.

meizoseismal curve
 * A curved line connecting the points of the maximum destructive energy of an earthquake shock around its epicenter.