The Aggregates & Recycling Information Network

Glossary: M

  • Macadam

    Uniformly graded stone compacted to form a road named after 19th century engineer John MacAdam.

  • Machine Tools

    Metal-cutting machines such as lathes, drills, grinders, planers etc.

  • Machine-hour

    The running of a machine or plant for one hour.

  • Magazine

    Premises registered in accordance with section 21 of the Explosives Act 1875; a magazine licensed in accordance with sections 6 to 8 or a store licensed in accordance with section 15 of the 1875 Act. 

    Also: explosives store

  • Magma

    Naturally occurring deep molten rock material from which igneous rocks are formed on cooling.

  • Magna Primer

    The trade name for a primer cartridge which incorporates, in addition to the primer charge, two Magnadet delay detonators and is designed for use in quarry blastholes. It is connected to the special exploder by passing the primary coupling wire through a hole in its centre.

  • Magnadet

    Trade name for a system of initiation of quarry blasts in which the detonator is electrically isolated from outside influences by coupling it, through its own transformer, to a special exploder which provides a high-frequency supply of approximately 15,000Hz. The system offers protection against: dc power sources, normal ac power sources, static electricity hazards, electromagnetic radiation and current leakage.

  • Magnetic Field

    The space surrounding a permanent magnet or a conductor carrying an electric current throughout which the forces produced by the magnet or current can be detected.

  • Magnetic Flux

    The lines of magnetic force which, in theory, make up a magnetic field.

  • Magnetic Separator

    A device for separating, by means of an electromagnet, magnetic particles in a slurry from the remainder of the particles in the mixture. Used in the recovery of medium in heavy-media separation.

  • Magnetic Surveying

    A method of geophysical prospecting using a magnetometer to measure variations in the Earth’s magnetic field over the area under investigation. Magnetic anomalies plotted on a map are used to indicate the probable position of rocks containing magnetic minerals in the sub-surface structure.

  • Magnetite

    An iron ore mineral, Fe3O4 which occurs as a primary constituent of most igneous rocks.

  • Magnetometer

    An instrument for measuring the intensity of the Earth’s magnetic field. It is used in geophysical prospecting when it may be carried in a low-flying aeroplane where large areas are being investigated.

  • Malleability

    The property of a metal which may be bent or hammered without breaking.

  • Man-hour

    The labour of one man for one hour.

  • Manager

    A person appointed by the owner as manager of a quarry or part of a quarry under either section 98, 102 or 103 of the Mines and Quarries Act 1954.

  • Manager’s Rules

    Rules made by the manager which lay down procedures which will ensure that operations at the quarry can proceed without endangering the workforce or the public.

  • Manganese Steels

    Steels which contain more manganese than is usually present in plain carbon steel. The steel containing 11% to 14% Mn is called austenitic manganese steel or Hadfield’s manganese steel. This steel possesses high strength and resistance to wear after work-hardening. Used for crusher jaws, gyratory crusher concaves and mantles, bucket teeth etc.

  • Mantle
    1. The cast steel liner, usually of manganese steel, which sits on the head of a gyratory crusher.
    2. The rock layer between the Earth’s crust and the core.
  • Marble

    Metamorphic rock produced from limestone by recrystallization caused by heat and pressure.

  • Marginal Costing

    An accounting technique whereby the effect on costs of a small increment or decrease in output may be estimated. Assuming that the change in output does not affect the elements comprising fixed costs, the marginal cost will be the variable cost per unit of output.

  • Marine Band

    A bed which contains marine fossils.

  • Marine-dredged Aggregates

    Sand and gravel obtained by dredging marine deposits which have been extensively and satisfactorily used in the manufacture of concrete. The chloride content must be checked frequently to reduce the risk of corrosion of steel reinforcement.

  • Marl

    A calcareous clay or mudstone.

  • Marshall Asphalt

    A widely used design for asphaltic concrete originally conceived by Bruce Marshall of the Mississippi State Highway Department.

  • Marshall Test

    An unconfined compression test on asphalt samples. The point of failure of the compacted mix specimen gives the stability value while the compression at this load gives the flow value.

  • Mass

    The quantity of matter in a body.

    Unit: kilogramme (kg)

  • Massive Rock

    Rock without stratification, cleavage or schistosity; particularly applied to igneous rock-bodies but can be used to describe sedimentary rocks with thick or obscured bedding.

  • Matrix

    The finer-grained material between the larger particles of a rock or the material surrounding a fossil or mineral.

  • Maximum Demand

    The highest value of the power or apparent power taken within the account period, eg month or year. Maximum demand is recorded by a maximum-demand indicator which shows the new maximum demand if the demand during any half-hour period exceeds the previous maximum.

  • Maximum-demand Tariff

    A two- or three-part tariff consisting of a maximum-demand charge and a unit (kWh) charge together with, in the case of the three-part tariff, a service (k VA) charge. The service charge is a fixed charge designed to cover the cost of the supply authority’s installation and is based on the required capacity.

  • Mean Value

    The arithmetic mean of the instantaneous values of a periodic quantity taken over half a cycle.

    Also: average value

  • Mechanical Advantage

    The ratio of load to effort. 

    Also: force ratio

  • Mega-

    A prefix indicating multiplication by a million.

    abbr. M

  • Megger

    Trade name for a range of insulation resistance testers.

  • MEL

    abbr. maximum exposure limit.

    The maximum concentration of airborne substance to which employees may be exposed under any circumstances.

    See also: OES

  • Member

    A part of a structural framework, eg a beam, a tie etc.

  • Mesh

    The aperture in a screen surface, or the size of the aperture.

  • Metamorphic Rock

    Rock which has been altered by the action of heat, pressure or migrating fluids acting separately or together.

  • Method Study

    The systematic recording and critical examination of existing and proposed ways of doing work, as a means of developing and applying easier and more effective methods and of reducing costs.

  • Metre

    The SI unit of length; equal to 39.37in.

    Symbol: m

  • MHO

    abbr. manual handling operation

  • Mica

    Complex silicates of aluminium and potassium which are constituents of plutonic and volcanic rocks and which are characterized by their perfect basal cleavage. Used in the electrical industry.

  • Micro-

    A prefix meaning one millionth.

    Symbol: µ

  • Micro-Deval Test

    The European standard test upon aggregates for resistance to wear. BS EN 1097 Part 1.

  • Microgranite

    Fine-grained rock of syenitic composition.

  • Micrometer Gauge

    A U-shaped instrument for accurately measuring small lengths.

  • Micron

    A one millionth part of a metre.

    Symbol: µ

  • Microwave

    A form of electromagnetic radiation of relatively long wave length most commonly employed for heating materials containing water moisture. Can also be the basis of communication systems.

  • Middlings

    An intermediate product, left after the removal of a clean concentrate and rejected tailing, which is usually subjected to further treatment.

  • Mild Steel

    Hot-rolled steel which, because of its relatively low carbon content (0.15% to 0.29%), cannot be hardened by quenching but is much more ductile than steel with a higher carbon content.

  • Milli-

    A prefix indicating one thousandth of a unit.

  • Millisecond

    The unit of measurement of short delay intervals, equal to 1/1000 of a second.

  • Millstone Grit

    Deltaic deposits of Upper Carboniferous period between Carboniferous limestone and coal measures, consists of alternating grits and shales.

  • Mineral

    A naturally occurring inorganic substance having definite physical and chemical properties.

  • Minerals And Waste Development Framework

    A portfolio of Minerals and Waste Development Documents providing the spatial planning framework for an area.

  • Minerals And Waste Development Plan Documents

    Minerals and waste spatial planning documents forming part of the Minerals and Waste Development Framework.

  • Minerals And Waste Local Plans

    Produced by County Councils under the old planning system, these documents set out the strategic planning policies for minerals and waste issues for the locality. These will be progressively replaced by the new style development plans under the new planning system.

  • Minerals And Waste Planning Authority

    An authority with responsibility for planning control over mineral working and waste management.

  • Minerals Policy Statement

    Replacing Minerals Planning Guidance notes, these statements lay down the national policy guidance for minerals planning, published by the Department of Communities and Local Government (formerly the Office of the Deputy Prime Minister).

  • Minimum Fusing Current

    The minimum current which will cause the fuse link to operate in a specified time under prescribed conditions.

  • Misfire

    A shot or any part of a shot, which fails to explode when an attempt is made to fire it, or where testing before firing reveals broken continuity which cannot be rectified.

  • Mix Design

    The choice and proportioning of aggregate, cement and water to produce a concrete with the required properties, the essential elements of which are usually durability and strength.

  • Mobile crusher
    Mobile Crusher

    A crusher that may be moved rather than fixed within the structure of a plant.  The machine is mounted in a frame which may have wheels (towed) or crawler tracks (self-propelled).

  • Mobile screen
    Mobile Screen

    A screen that is mounted in a frame which may have wheels or crawler tracks.

  • Modular Screen Decks

    Screen decks comprised of numerous small panels held in position by quickrelease pegs, making for easier handling, the ability to localize replacement of worn sections and the use of a combination of apertures where required.

  • Moh’s Scale Of Hardness

    An indication of scratch resistance based on the relative hardness of 10 common minerals which, in order of increasing hardness, are: 1 talc, 2 gypsum, 3 calcite, 4 fluorite, 5 apatite, 6 orthoclase, 7 quartz, 8 topaz, 9 corundum, 10 diamond.

    Also: hardness of rock

  • Mole Drain

    A drain cut by drawing a mole plough (a vertical blade with a horizontal bullet-shaped cutter at its lower end) attached to a tractor, through the soil.

  • Moment Of A Force

    The turning effect of a force. The moment of a force about a point is the product of the force and the perpendicular distance of its line of action from the point.

    Units: newton-metres (Nm)

  • Momentum

    The product of the mass of a body and its velocity.

    Units: kgm/s

  • Monitor

    [img_assist|nid=11977|title=|desc=|link=none|align=right|width=158|height=76]A device for directing a jet of water at high pressure to break down a mineral deposit, eg china clay.

  • Moraine

    Unsorted, unstratified glacial drift; the material usually forms two lateral moraines parallel to the sides of the glacier. The ridge formed at the end of a glacier when the ice melts is called a terminal moraine.

  • Mortar

    Mixture of fine aggregate with water and cement or lime, or a combination of both, that hardens after application and is used for jointing.

  • MOT 1

    A common term used to refer to SHW type 1 sub-base, the product defined by the Specification for Highway Works which is used to provide structural support below roads and also for buildings.

  • MOT 2

    A common term used to refer to SHW type 2 subbase, the product defined by the Specification for Highway Works which is used to provide structural support below roads and also for building.

  • Motor Enclosure

    Structure containing an electric motor. The numerous types of enclosure include: drip-proof, totally enclosed, flameproof and pipe-ventilated.

  • Motor Rating

    The whole of the rated values and operating conditions of electrical machines and equipment. The rating of a motor may be stated as being the output power of the motor under specified working conditions, eg cooling air temperature less than 40°C, without the temperature rise exceeding a specified value. 

    Also: rating

  • Motorized Scrapers

    Single- or twin-engined bowl scrapers which are hydraulically operated. They are used on sites where large quantities of material have to be removed quickly and ground conditions are relatively firm.

  • Movement Ratio

    The ratio of the distance moved by the effort to the distance moved by the load.

    Also: velocity ratio

  • MPA
    1. abbr. Mineral Products Association. Trade association for the aggregates, asphalt, cement, concrete, lime, mortar & silica sand industries. Formed in 2009 by the merger of the Quarry Products Association (QPA), British Cement Association (BCA) and The Concrete Centre
    2. mineral planning authority
  • Muckpile

    Rock pile of stone fragmented by a blast.

    See also: rock pile

  • Mudcap

    In secondary blasting, a charge of explosive fired in contact with the surface of a rock, usually covered with a quantity of mud or other similar substance.

    See also: plaster shooting

  • Mudstone

    A sedimentary rock consisting largely of hardened clay minerals, blackish and without lamination.

  • Mulch

    Any substance spread or allowed to remain on the soil surface to conserve soil moisture and shield soil particles from the erosive forces of raindrops and runoff.

  • Multi-deck Screen

    A screen with two or more superimposed decks mounted rigidly within a common frame.

  • Multi-row Blasting

    A series of blastholes arranged in rows parallel to the free face. More common in surface mining than in rock quarrying.

  • Multi-strand Rope

    Wire rope consisting of two or more layers of round strands. The alternate layers of strands are laid in opposing directions to counteract torsional stress and produce a rope with nonspinning characteristics.

  • Multigrade Oils

    Oils which satisfy service requirements at both low and high temperatures so far as viscosity is concerned. They are allocated a compound SAE number, incorporating the viscosity grading at low temperature (first number) and that at high temperature (second number).

  • Multiplying Constant

    In tacheometer work, the constant by which the staff intercept is multiplied to obtain the distance between the instrument and the staff.

  • Muscovite

    A light-coloured mineral of the mica group, common in igneous and metamorphic rocks and in some sandstones.

  • Mutual Inductance


    The ratio of the magnetic flux-linkage of an electric circuit and a current. Self-inductance refers to inductance in which the current is that of the circuit itself and mutual-inductance where the linkage results from the current in another circuit.

    Symbol: H

    Unit: Henry

    Also: mutual inductance