Glossary: H

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

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.

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.

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

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

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

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

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.

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.

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

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

A prefix denoting one hundred times.

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

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

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.

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.

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

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

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

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

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

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

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.

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

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

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

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

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.

An instrument for measuring the relative humidity of the atmosphere.

Igneous rocks intruded at intermediate depth.