The Aggregates & Recycling Information Network

Glossary: H

  • Hade

    The angle of inclination of the plane of a fault to the vertical.

  • Haematite

    Iron oxide, specular iron ore and kidney ore are varieties.

  • Hammer Mill

    An impact crusher consisting of a rotor, rotating at high speed, to which hammers are attached by hinge pins.

  • Hand Sprayer

    A binder distributor in which the spray is directed on to the surface by means of a spray lance. Pressure is provided by a hand- or power-driven pump.

  • Hanging Wall

    The rock immediately overlying a mineral deposit.

  • Hard-facing

    The application, usually by welding, of a layer of hard material on the surfaces of the parts of machinery which are subject to heavy wear, eg shovel buckets.

  • Hard-standing

    A hard surface used for parking vehicles.

  • Hardcore

    Recovered stone, broken brick or the like which, when spread and compacted, can be used as a rough filling material.

  • Hardness Of Rock

    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: Moh’s scale of hardness

  • Hardware

    General term for all electrical and mechanical components of a computer or data-processing system.

  • HaSaWA

    abbr. Health and Safety at Work etc Act 1974.

  • Hatching

    The parallel lines filling areas in a drawing to indicate for instance, differences in materials.

  • Haul

    The distance quarry or opencast products must be moved to the treatment plant or dump.

  • Hazard

    The potential to do harm to the health and safety of any person.

  • Head
    1. The potential energy per unit weight of fluid above a datum, ie the height in metres of the water level above that point. In theory this should include its actual potential energy, its kinetic energy and its pressure energy.
    2. Geological term, describing scree-like accumulations of rubble formed under sub-arctic conditions.
  • Health And Safety Document

    An essential requirement of the Quarry Regulations 1999 containing all matters related to safety, eg policy, appointments, management structure, risk assessments, rules, inspections and procedures.

  • Heaped Capacity

    The SAE heaped capacity for loaders and haulers is the capacity assuming the load above the sides has a slope of 2:1 and that of scrapers when the slope is 1:1.

  • Heat Exchange

    The process of transfer of heat energy from one stream of matter (solid or fluid) to another by radiation, convection or conduction, to effect a change in temperature of the two streams.

  • Heat Exchanger

    Equipment for effecting heat exchange between two fluid streams without their admixture, for the purpose of cooling one, or for the conservation of heat from a waste stream.

  • Heat Treatment

    Any heating or controlled cooling of a metal to change its properties.

  • Heater Planer

    A road heater fitted with cutters and used for removing irregularities or a course of material from a road surface by planing or milling action prior to resurfacing; the process is preceded by softening of the surface by heat.

  • Heavy-media Separation

    A mineral-processing operation in which mineral fragments can be separated on the basis of differences in density by being allowed to sink or float in a medium of intermediate density. The medium consists of a suspension of a finely ground high density solid (eg magnetite) in water.

    abbr. HMS

    Also: dense-media separation

  • Hectare

    An area equal to 10,000m2.

  • Hecto-

    A prefix denoting one hundred times.

  • Helical Conveyor

    A conveyor consisting of a central shaft with helical paddles or a complete helical screw rotating within a stationary tube or trough filled with the material being conveyed. 

    Also: screw conveyor

  • Henry

    The inductance of a closed circuit in which an electromotive force of one volt is produced when the electric current in the circuit varies uniformly at the rate of one ampere per second.

    Symbol: H

  • Hertz

    The unit of frequency: one cycle per second.

    Symbol: Hz

  • High-tensile Steel

    Steel with a higher yield point than that of mild steel and which is used, where necessary, for engineering structures or machine parts.

  • Highwall

    In opencast mining, the wall of the pit at which work is in progress; the coal or ore and the overburden above it.

  • Historical Costing

    The form of costing concerned with costs which have been incurred and recorded. Comparisons are made with costs during similar accounting periods in the past.

  • HM Inspector

    A Crown official with statutory powers of inspection, investigation, inquiry and enforcement of safety law.

  • HMS

    abbr. heavy-media separation

    A mineral-processing operation in which mineral fragments can be separated on the basis of differences in density by being allowed to sink or float in a medium of intermediate density. The medium consists of a suspension of a finely ground high density solid (eg magnetite) in water.

  • HMSO

    abbr. Her Majesty’s Stationery Office.

  • Hoggin

    A naturally occurring mixture consisting mainly of gravel and sand and containing sufficient clay to bind the mixture together when rolled.

  • Holdback

    A device used on an inclined conveyor to prevent the loaded belt from running downhill in the event of a power failure.

  • Holding-down Bolt

    A bolt with its threaded end projecting above the foundation and secured so as to hold down a steel structure against wind loads or machinery against its vibration. 

    Also: anchor bolt and foundation bolt

  • Holocene

    An alternative term for the Recent epoch.

  • Hooke’s Law

    Within the elastic limit, the extension of a material is proportional to the applied stress.

  • Hornblende

    Common amphibole containing calcium, magnesium and iron.

  • Hornfels

    Thermally metamorphosed rock containing substantial amounts of rock-forming silica minerals.

  • Horsepower

    A practical unit of power approximately equal to 746 watts.

    Symbol: hp

  • Hutch

    The part of a jig situated below the screen plate in which the controlled pulsating movement of water takes place.

  • Hydrated Lime

    Product obtained by slaking quicklime with a controlled quantity of water, usually sieved, dried and bagged.

  • Hydration

    The addition of water to anhydrous minerals, resulting in the production of hydrous minerals, eg anhydrite is converted in to gypsum.

  • Hydraulic

    Relating to the flow of fluids.

  • Hydraulic Accumulators

    An accumulator consists of a chamber into which hydraulic fluid enters under pressure and in so doing compresses either a gas or a spring. A fall in the pressure at the inlet results in fluid being forced back into the system by the compressed gas or spring.

  • Hydraulic Lime

    Quicklime containing sufficient soluble silica, alumina, etc to enable it to set in the presence of water. Hydraulic lime is said to be emminently (classified by BS EN 459-1 as NHL 3.5 and NHL5), moderately (NHL 3.5) or feebly (below the strength for BS EN 459 classification for NHL) hydraulic.

  • Hydraulic Mining

    A method of winning mineral by washing it with high-pressure jets of water, and subsequently transporting it in flumes or pipes.

  • Hydraulic Motors

    Multi-cylinder reciprocating machines which are essentially similar units to hydraulic pumps.

    See also: gear pump, piston pumps and vane pump

  • Hydraulic Reservoir

    A reservoir which caters for varying oil volumes in the system as cylinders extend or compress, also for changes in volume due to temperature.

  • Hydraulic Test

    A test for boilers, pipes, pressure vessels etc by filling them with water to the required pressure.

  • Hydrocyclone

    A conical classifying device into which pulp is fed so as to take a circular path. Coarser and denser fractions of solids report to the apex of the cone, while finer particles overflow from the central vortex. Cyclones are also used for dewatering and in the removal of dust particles from air and other gases. 

    Also: cyclone

  • Hydrodynamics

    The use of the energy of a fluid in motion, as in such as hydraulic couplings and torque converters.

  • Hydrographical Surveying

    Surveying of bodies of water at the coast, estuaries and rivers, but may also be applied to lagoons, flooded workings etc.

  • Hydrology

    The study of water on the Earth’s surface.

  • Hydrometer

    An instrument which, when floated in a liquid, gives a measurement of its relative density by the level on the stem to which it is submerged.

  • Hydrostatics

    The study of forces arising from the presence of fluids, eg the use of pressure energy to transmit force as in a hydraulic press.

  • Hygrometer

    An instrument for measuring the relative humidity of the atmosphere.

  • Hypabyssal

    Medium-grained, intrusive igneous rocks forming dykes and sills.

  • Hyperbyssal

    Igneous rocks intruded at intermediate depth.

  • Hz

    abbr. hertz 

    The unit of frequency: one cycle per second.