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This glossary is intended to explain some of the technical terms used on the MineralsUK website.



Adit – Common mining term for a horizontal to sub–horizontal tunnel driven into a hillside to access an ore body.

Agglomerate – A volcanic rock consisting of fragments of pyroclastic rocks more than 2 cm in size.

Alkaline – A term applied to igneous rocks which are characterised by relatively high concentrations of sodium and potassium.

Allotrope – The occurrence of an element in many forms.

Alluvial – Deposits of sediment, usually sand and gravel, transported and deposited by a river.

Anode – A plate of metal cast in a shape suitable for refining by the electrolytic process.

Archean – Period of geological time that is the older of the two main Precambrian divisions. Ends 2500 million years ago.

Argillaceous rocks – A group of detrital, fine grained, sedimentary rocks subdivided into silt grade (particle size range 1/16 to 1/256 mm) and clay grade (particle size < 1/256 mm).

Amorphous graphite – Anhedral and very fine-grained crystalline graphite without visible crystallinity.

Arsenide – A mineral formed by the combination of arsenic with another chemical element e.g. sperrylite, PtAs2.

Autocatalyst – A cylinder made from ceramic or metal formed into a fine honeycomb and coated with a solution of chemicals and platinum–group metals. It is used to control the emissions of pollutants, such as carbon monoxide, oxides of nitrogen and hydrocarbons, produced by motor vehicle exhaust systems. It is mounted in the exhaust system between the engine and the silencer and converts the noxious substances into harmless species.


Barite – A white, yellow or colourless mineral, BaSO4. The principal ore of barium used in paints, drilling muds and as a filler for paper and textiles. Syn: baryte, barytes.

Basic – Describes an igneous rock with a relatively low silica content (between 45–52% SiO2). Basic rocks are relatively rich in iron, magnesium and calcium and thus include most mafic rocks.

Battery Raw Materials – Minerals and metals used as the key constituents of a battery including: Aluminium, cobalt, graphite, lithium, manganese, nickel, phosphate, sulphur and vanadium.

Bench – Term used to describe the various working levels in a quarry, created and controlled by variations in bed depth as the worked quarry face is developed.

Beneficiation – The process of concentration of the valuable components of an ore or other mineral commodity. Commonly includes multiple stages such as crushing, grinding, washing, screening, flotation, roasting, etc.

Bituminous – Type of coal that contains a naturally occurring tar–like hydrocarbon mineral of indefinite composition. It ranges in consistency from a thick liquid to a brittle solid.

Boghead coal – A type of coal comprising mostly algal material with fungal matter. See sapropelic.

Breccia – A rock that has been mechanically, hydraulically or pneumatically broken into angular fragments and re–cemented. (brecciated, adj).

Building stone – Naturally occurring rocks of igneous, sedimentary or metamorphic origin which are sufficiently consolidated to enable them to be cut or shaped into blocks or slabs for use as walling, paving or roofing materials in the construction of buildings and other structures. The principal building stones include igneous rocks (such as granite), massive bedded sandstones, limestones and metamorphic rocks (such as marble and slate). Also known as Dimension stone.


Calcination – The process of roasting metallic concentrates to remove sulphur prior to smelting.

Calcite – A very common rock forming mineral comprising calcium, carbon and oxygen (CaCO3).

Cambrian – Period of geological time from 545 to 495 million years ago. Marks the beginning of the Paleozic Era.

Cannel coalSapropelic coal type.

Carat – Term used in gemology to describe the weight of a semi–precious or precious stone (1 carat = 2.4 g). Derived from the ancient practice of using carob seeds as comparative weights for gems.

Carbonate – A mineral characterised by a fundamental structure of CO3. Common examples include calcite, dolomite, magnesite and siderite.

Carbonatite – A magmatic rock consisting of calcium carbonate, usually associated with nepheline–syenite systems.

Carboniferous – Period of geological time from 354 to 292 million years ago. So named because of the globally extensive occurrence of coal and limestone (CaCO3) that was formed during this time. In the UK the Lower Carboniferous is dominated by marine sediments. Upper Carboniferous rocks are almost entirely fresh–water and lacustrine sediments. The bulk of coal deposits in the UK occur in Upper Carboniferous strata.

Cathode – A plate of metal produced by electrolytic refining. Subsequently melted and cast into bars, ingots, etc.

Cenozoic Era – Period of geological time extending from 65 million years ago to the present.

Chert – Sedimentary rock that is ultra–fine grained and composed almost entirely of silica. May be of organic or inorganic origin.

Coal – A combustible rock composed of lithified plant remains.

Cobalt – A lustrous, silvery-grey metal with many physical and chemical properties that make it useful in a wide variety of chemical and metallurgical applications.

Coking coal – Trade category of coal that is used in the steel industry to de–oxidise iron ore in the blast furnace.

Core strategy: Sets out the long-term spatial vision for the local planning authority area, the spatial objectives and strategic policies to deliver that vision. The core strategy will have the status of a development plan document.

Cretaceous – Period of geological time from 142 to 65.5 million years ago. Marks the end of the Mesozoic Era.

Critical raw material – Raw materials of economic importance and a high-risk associated with their supply.


Dalradian – Late Precambrian metamorphosed marine sedimentary rocks found in the Grampian Highlands of Scotland and in Ireland.

Development plan: As set out in Section 38 of the Planning and Compulsory Purchase Act 2004, an authority's development plan consists of the relevant regional spatial strategy (or the spatial development strategy in London) and the development plan documents contained within its local development framework.

Development plan documents: Spatial planning documents that are subject to independent examination, and together with the relevant regional spatial strategy, will form the development plan for a local authority area for the purposes of the Act. They can include a core strategy, site specific allocations of land, and area action plans (where needed). Other development plan documents, including generic development control policies, can be produced. They will all be shown geographically on an adopted proposals map. Individual development plan documents or parts of a document can be reviewed independently from other development plan documents. Each authority must set out the programme for preparing its development plan documents in the local development scheme.

Devonian – Period of geological time from 417 to 354 million years ago.

Diamagnetic – Having a small negative magnetic susceptibility.

Dimension stone - See Building stone.

Dolomite – A common rock forming mineral comprising calcium, carbon, magnesium and oxygen (CaMg(CO3)2.


Electrolytic – The process of extracting metal based on passing an electric current through a solution containing dissolved metals, causing the metals to be deposited on the cathode.

Evaporite – A sedimentary rock composed mainly of minerals produced by evaporation, normally from an enclosed body of seawater or a salt lake. Minerals formed in this way include gypsum, rock salt, and various nitrates and borates.

Exinite – One of the three types of macerals that make coal.

Extrusive – Describes igneous rocks that have been formed by solidification of magma on or above the Earth's surface.


Ferromagnesian – Describes rock–forming silicate minerals which contain essential iron (Fe) and/or magnesium (Mg). The most common ferromagnesian minerals include olivine, pyroxene, amphibole and mica.

Flake graphite – Crystalline graphite of flaky or platy morphology.

Fluorite – A common mineral comprising, when pure, of 51.1% calcium and 48.9% fluorine.

Fluorspar – The commercial name for the mineral fluorite.

Footwall – The name given to the host rock of an ore deposit that is physically below the ore deposit.

Froth flotation – A process by which some mineral particles are induced to become attached to bubbles and thereby to float, while others sink. Thus valuable minerals in an ore are separated from other components and concentrated.


Gabbro – A coarse–grained mafic igneous rock consisting of plagioclase feldspar and pyroxene. Olivine may also be a major constituent, while hornblende, biotite, quartz, magnetite and ilmenite are common minor phases.

Gangue – The undesirable or unwanted minerals in an ore deposit.

Gneiss – Coarse-grained, granular, banded rock of metamorphic origin.

Goaf – Name given to the collapsed hanging wall resulting from longwall mining.

Granite – A pale-coloured, coarsely crystalline igneous rock rich in silica (quartz) and alkali feldspar.

Graphene – An allotrope of carbon comprised of a single layer of carbon atoms. Many layers of graphene form graphite.

Graphite – A form of carbon that occurs as black to steel grey, lustrous flaky aggregates, disseminated in metamorphic rocks or as veins with a fibrous or foliated texture.


Hanging wall – The name given to the host rock of an ore deposit that is physically above the ore deposit.

Highwall mining – Mining method used to maximize the output of an open–pit coal mine. Remotely operated cutting or boring machines are used to penetrate the coal seam at the foot of the highwall (the final wall in an open–pit) to extract coal.

Holocene – Period of geological time from 11,500 years ago to the present day. The youngest epoch and series of the Cenozoic Era.

Humic – Type of coal that is predominantly composed of mixed plant debris. These typically contain the maceral minerals. See also sapropelic.

Hydrometallurgy – The treatment of ores by wet processes, resulting in the dissolution of a particular component and its subsequent recovery by precipitation, adsorption or electrolysis.


Igneous – One of the three main groups of rocks on Earth. They have a crystalline texture and appear to have consolidated from a silicate melt (magma).

Inertinite – One of the three macerals that make coal.

Intrusion, n. – A body of igneous rock emplaced into pre–existing rocks, either along some structural feature such as a fault or by deformation and rupturing of the invaded rocks.
(intrusive, adj).


JORC – Australasian mineral resource classification (Joint Ore Reserves Committee).

Jumbo – Industrial size standard for flake graphite of +500 microns.

Jurassic – Period of geological time from 205.1–142 million years ago.


Kaolin – Group of pale coloured clay minerals. In the UK kaolin is an industrial mineral extracted from kaolinised granites in south–west England. It is used as a paper filler and coater, and for high grade ceramics and pottery (china clay).

Karat – The proportion of pure gold in an alloy. Pure gold is 24 karat, with lesser quantities of gold represented by a fraction. For example, 18 karat gold is 18/24 or 75% gold, 25% non–gold alloying metal.


Leach – A chemical process in which certain components of the ore are dissolved to extract and concentrate valuable minerals.

Lenticular – Lens shaped body of rock.

Limestone – Any sedimentary rock consisting mostly of carbonates (calcite and/or dolomite).

Lithium – A soft, silvery-white to grey alkali metal with a metallic lustre when fresh. It is highly reactive and in air quickly tarnishes to a dull silvery-grey and then black.

Local development document: The collective term in the Act for development plan documents, supplementary planning documents and the statement of community involvement.

Local development framework: The name for the portfolio of local development documents and related documents. It consists of development plan documents, supplementary planning documents, A statement of community involvement, the local development scheme and annual monitoring reports. It may also include local development orders and simplified planning zone schemes. Together all these documents will provide the framework for delivering the spatial planning strategy for a local authority area.

Local development scheme: Sets out the programme for preparing local development documents. All authorities must submit a scheme to the Secretary of State for approval within six months of commencement of the Act.

Lode – Mining term for a mineralized vein (used irrespective of whether the vein can be economically extracted).

Longwall mining – Type of mining that is typically found in underground coal mines. The coal seam is mechanically extracted and the hanging wall is allowed to collapse, under controlled conditions, to fill in the void. The collapsed hanging wall material is known as the goaf.


Macerals – In coal, the organic equivalent of minerals. These are typically vitrinite, exinite and inertinite.

Mafic – composed of one or more ferromagnesian (iron–magnesium), dark–coloured minerals, such as olivine and pyroxene, in combination with quartz, feldspar or feldspathoid minerals.

Magnetic susceptibility – A measure of the degree to which a rock is attracted to a magnet. A dimensionless constant which determines the degree to which a body is magnetised. Used in the interpretation of geophysical magnetic surveys.

Marble – Metamorphosed (or recrystallized) limestone formed by extremes of heat and pressure, commonly occurs in highly colourful, variegated forms.

Marl – A calcareous mudstone.

Matte – A product of a smelter that is composed of a metal, or metals, combined with sulphur. Requires further treatment to remove the sulphur.

Mesozoic Era – Period of geological time from 250 to 65.5 million years ago. Subdivided into the Triassic, Jurassic and Cretaceous periods.

Miocene – Period of geological time from 23.8 to 5.32 million years ago.

Mississippi Valley type, (MVT) – A type of stratabound deposit of lead and/or zinc in carbonate rocks, as occurring in the Mississippi valley, USA.

Mohs hardness – A qualitative order scale that characterises the scratch resistance of various minerals by the ability of harder material to scratch softer material.

Mudstone – Fine grained sedimentary rocks that are similar to shales in their non–plasticity, cohesion and low water content but lack fissility.


Natural cokeCoal that has been carbonized by contact with an igneous intrusion or natural combustion.

Natural gas – Hydrocarbons that occur as a gas or vapour. Usually methane, but propane may be present.

Neogene – Part of the Cenozoic Era, comprising the Miocene and Pliocene epochs from 23.8 to 1.81 million years ago.

Nickel – A silvery-white, lustrous metallic element, which belongs to the transition metals and is relatively abundant in the Earths crust.


Occurrence – Locality where a mineral is found.

Oligocene – Period of geological time from 28.5 to 23.8 million years ago.

Ophiolite – A distinctive assemblage of mafic and ultramafic igneous rocks which occur in sequence from a basal ultramafic complex upwards to a gabbroic complex, a mafic sheeted–dyke complex and an uppermost mafic volcanic complex. Commonly associated with deep–water sediments such as shales and cherts. Generally interpreted to be derived from oceanic crust and upper mantle. Ophiolites may contain important deposits of chromite, copper and the platinum–group elements (PGE).

Ordovician – Period of geological time from 495 to 440 million years ago.

Overburden – Material which includes soft sediment and weathered bedrock which must be removed to access the dimension stone beds.


Paleogene – Part of the Cenozoic Era comprising the Paleocene, Eocene and Oligocene epochs, from 65.5 to 23.8 million years ago.

Paleozoic Era – Period of geological time from 545 to 245 million years ago. Subdivided into the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian Periods.

Pegmatite – A very coarse–grained igneous rock characterized by crystals > 3 cm in length.

Peridotite – A class of ultramafic rocks consisting of predominantly olivine, with or without other ferromagnesian (Fe–Mg) minerals.

Permian – Period of geological time from 280 to 255 million years ago, marks the end of the Paleozoic Era. Globally important source of coal.

Permitted reserves – Mineral deposits with the benefit of planning permission for extraction.

Planning permission – Formal approval sought from a council, often granted with conditions, allowing a proposed development to proceed. Permission may be sought in principle through outline plans, or be sought in detail through full plans.

Platinum-group metals – The six chemical elements referred to as the platinum-group metals (PGM) or platinum-group elements (PGE): Platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os).

Pliocene – Period of geological time from 5.3 to 1.81 million years ago.

Porphyry deposit – A mineral deposit comprising veinlets and disseminated grains of ore minerals, commonly hosted by an igneous rock, known as a porphyry, in which relatively large conspicuous crystals (phenocrysts) are set in a fine–grained groundmass. Porphyry deposits are important sources of copper, molybdenum and gold.

Precambrian – Extensive period of geological time used literally as ‘before the Cambrian’. Contains around 90% of all geological time and ends approximately 545 million years ago.

Proterozoic – A period of geological time that is the uppermost of the two main Precambrian divisions. Runs from 2500 to 545 million years ago.

Pyroclastic – Fragmental volcanic material that has been blown into the atmosphere by an explosive eruption.

Pyrometallurgical – The treatment of ores by processes involving heating.


Quarrying (mining) – The extraction of rock from an open pit site.

Quartzite – sandstone consisting of almost pure quartz in the form of silica grains and pervasive intergranular silica cement.

Quaternary – The uppermost part of the Cenozoic Era from 1.81 million years ago to present day.


Rare Earth Elements (RREs) – Th rare earth elements (REE) are a group of 17 chemically similar metallic elements that include the 15 lanthanides, spanning atomic numbers 57 (lanthanum) to 71 (lutetium), together with scandium and yttrium. As refined metals the REE are typically lustrous, dark grey to silvery in appearance.

Refractory – A general term for a material that resists chemical or physical change.

Refractory ore – Ore from which it is difficult to extract the valuable constituents. May require special treatments, such as pressure leaching, to recover the valuable minerals.

Regional spatial strategy: Sets out the region's policies in relation to the development and use of land and forms part of the development plan. Planning Policy Statement 11 ‘Regional Spatial Strategies' together with the document ‘Planning Policy Statement 11: Regional Planning Strategies (2004), technical amendments’ provide detailed guidance on the function and preparation of regional spatial strategies. Guidance will change if the ‘Draft Policy Statement on Regional Strategies’ is approved as scheduled in early 2010.

Regolith: Regolith is a layer of loose superficial material covering the underlying bedrock.

Resource – Defined as the natural concentration of minerals that are, or may become in the future, of potential economic interest due to their inherent properties and their sufficient quantity to make it of intrinsic economic interest.

Reserve – The part of a mineral resource, which has been fully evaluated and is deemed commercially viable to work.

ROM ore – (Run of mine) ore that's mined and ready to go to the processing plant.

Room and Pillar mining – Common mining method most suitable for thick, flat lying, laterally homogeneous, ore bodies. Pillars of ore are left behind after mining to support the hanging wall. Also called Pillar and Stall mining.

Room and Pillar mining – Common mining method most suitable for thick, flat lying, laterally homogeneous, ore bodies. Pillars of ore are left behind after mining to support the hanging wall. Also called Pillar and Stall mining.


Saprolite – Geochemically weathered rock, typically formed in the lower zones of soil profiles by retaining textural and structural features of the parent material.

Sapropelic – Type of coal that is composed mostly of algae and plant spores.

Schist – A highly micaceous metamorphic rock which can be split along its characteristic undulating laminae.

Sedimentary exhalative (Sedex) – An ore deposit formed from hydrothermal fluids discharged onto the sea–floor and hosted by sedimentary rocks such as black shale, siltstone and chert. Deposits comprise sheets or lenses of fine–grained laminated sulphides. Sedex deposits are important sources of zinc, lead and silver.

Sedimentary rocks – All rock types formed by the weathering, erosion and deposition (or sedimentation) of inorganic (quartz, feldspar and rock fragments) and growth, decay and deposition of organic (bioclasts) grains in rivers, lakes or the sea or by deposition from wind-borne sources (volcanic ash, sand dunes).

Shale – A fine–grained, indurated, sedimentary rock of detrital origin formed by the consolidation of clay, silt or mud. Characterised by finely stratified structure and/or fissility approximately parallel to bedding. Composed mainly of clay minerals and detrital quartz.

Silurian – Period of geological time from 440 to 417 million years ago.

Sinter – Roasting of fine–grained ore to produce larger particles for further treatment.

Skarn – Metamorphic rocks formed around an igneous intrusion where it comes into contact with limestone or dolomite. Many skarns contain iron ore and various sulphide minerals and are important sources of metals including tin, tungsten, copper, lead, zinc, iron, gold, silver and molybdenum.

Slate – Fine grained metamorphic rock with well developed cleavage which enables the stone to be split easily into thin slabs or sheets.

Steam coal – Trade category of bituminous coal that is used for burning in power stations and other industrial/domestic uses.

Stope – Mining term for the underground void left after ore extraction has taken place.

Stratabound – An ore deposit that is confined to a single stratigraphical bed or horizon but which does not constitute the entire bed.

Stratiform – An ore deposit that occurs as a specific stratigraphic (i.e. sedimentary) bed.

Sulphide – A mineral formed by the combination of sulphur with another chemical element. Most economic deposits of non–ferrous metals occur as sulphide minerals e.g. galena, PbS; sphalerite, ZnS; chalcopyrite, CuFeS2.

Supplementary planning documents – Provide supplementary information in respect of the policies in development plan documents. They do not form part of the development plan and are not subject to independent examination.


Telluride – A mineral formed by the combination of tellurium with another chemical element e.g. calaverite, AuTe2.

Travertine (or tufa) – Fine-grained limestone deposited by chemical precipitation from a lime-saturated solution, commonly sold as a marble.

Triassic – Period of geological time from 250 to 205.1 million years ago. Marks the beginning of the Mesozoic Era.

Tungsten – A lustrous greyish-white metal with some unique properties including a high melting point (3422oC) and very high density (19.3 g/cm3).


Ultrabasic – Describes an igneous rock containing less than 45% silica (SiO2), including most ultramafic rocks.

Ultramafic – Composed chiefly of ferromagnesian (Fe–Mg) minerals, such as olivine and pyroxene.


Vein – A tabular or sheet–like assemblage of minerals that has been intruded into a joint or fissure in rocks.

Vitrinite – One of the main groups of macerals that make coal.

Volcanogenic massive sulphide, VMS – An ore deposit typically comprising a lens of massive sulphide minerals (>60% sulphide) formed by volcanic processes normally on the sea–floor. VMS deposits are important sources of copper, lead and zinc.


Wall rock – An economic geology term used to describe the rock adjacent to an accumulation of ore minerals (veins, layers, disseminations, etc).

Workings – The current or past underground or surface openings and tunnels of a mine. More specifically, the area where the ore has been extracted.


Xenolith – A discrete and recognizable fragment of country rock in an igneous intrusion.


Yellow copper ore – A historically common, but now rare, mining term for the mineral chalcopyrite.


Zoning – In economic geology, the spatial distribution of distinct mineral assemblages or chemical elements associated with an ore–forming process.