Glossary of Geological Terms

Aeromagnetics

Measurement of the earth's magnetic field from a surveying aircraft, for the purpose of recording the magnetic characteristics of rocks.

Alluvium/alluvial

Recent surficial water-lain sediments.

Alteration zone

Zone within which rock-forming minerals have been chemically changed.

Anomalism

Said of geochemical and geophysical data, which deviates from regularity.

Anthropological

Of or having to do with anthropology.

Anticline

A fold that is convex up or to the youngest beds.

Archaean

The oldest rocks of the Precambrian Era, older than about 2500 million years.

Arsenic

A mineral, the native element, occurring in grey masses.

Arsenopyrite

A mineral, FeAsS.

Assay

Is a process by which the elemental concentrations of a rock or sample are measured by a laboratory.

Banded Iron Formation (BIF)

Chemical sedimentary rock composed mainly of finely alternating layers of silica and iron oxide.

Barite

The principal ore of barium.

Base metals

The more common and chemically active metals, e.g. lead, copper, zinc, nickel.

Basin

An extensive depressed area into which the adjacent land drains.

Bedrock

Solid rock underlying surficial deposits.

Bismuth

A brittle metallic chemical element.

BLEG

Bulk Leach Extractable Gold, an analytical method of gold analysis.

Biotite

A generally dark coloured iron, magnesium and potassium rich mica.

Boudinage

A structure in which beds set in a yielding matrix to form rounded sausage-like segments.

Breccia

Rock containing angular fragments enclosed in a matrix.

Calcrete

Hardened deposit of calcium carbonate which cements together other materials including gravel, sand and clay.

Carbonate

A salt or ester of carbonic acid; a compound containing the radical CO3.

Chert

Very fine grained rock composed of silica.

Chlorite

A platy hydrous silicate related to mica.

Chromite

Iron magnesium chromium oxide belonging to the spinel group often found in ultramafic intrusive rocks.

Clastic

Rocks composed of fragmental material derived from pre-existing rocks.

Cobalt

A hard silver-white metallic chemical element.

Colluvial/Colluvium

Comprises alluvium containing angular fragments of the original rock source.

Copper

Copper is a ductile metal with excellent electrical conductivity that has the symbol Cu.

Cretaceous

Third and latest of the periods in the Mesozoic era.

Craton

A relatively immobile part of the earth, generally of large size.

Deformation

Any change in the original form or volume of rocks produced by tectonic forces.

Deposition

The laying down or precipitation of potential rock forming material.

Diamond drilling

Method of obtaining cylindrical core of rock by drilling with a diamond-set or diamond-impregnated bit.

Dip

The angle strata or planar feature is inclined from the horizontal.

Disseminated

Particles scattered throughout the rock.

Dolomite

A common rock forming mineral with carbonate.

Dolerite

A medium grained mafic intrusive rock composed mainly of pyroxene and plagioclase.

Drainage

The processes of discharge of water from an area by stream or sheet flow and removal of excess water from soil by downward flow.

Electromagnetic (EM)

A geophysical technique whereby transmitted electromagnetic fields are used to energise and detect conductive material beneath the earths surface.

Extrusive

Pertaining to igneous rocks ejected at the earth's surface.

Facies

Assemblage of sedimentary or metamorphic rocks formed under similar conditions of temperature and pressure.

Fault

A fracture in rock along which there has been relative displacement of the two sides either vertically or horizontally.

Felsic

Descriptive of light coloured rock containing an abundance of the mineral feldspar (generally potassium rich) and quartz.

Ferruginous

Containing the element iron.

Fold

A bend in strata or any planar structure.

g/t

Grams per tonne.

Geochemistry

The study of the abundance of elements in rocks by chemical methods.

Geological model

The interpretation of geological data.

Geophysical

Describing the prospecting methods, which seek to locate mineral deposits by direct or indirect measurements of a large range of geophysical properties of the deposits or the rocks associated with them.

Gossan

A surface capping of hydrated oxides of iron formed by weathering of metallic sulphides.

Granite

A plutonic rock consisting essentially of alkalic feldspar and quartz.

Granitoid

A field term for a coarse grained felsic rock resembling granite.

Gravity survey

Acquire survey co-ordinates and gravity readings for a grid of stations from the survey area.

Greenschist facies

Metamorphic rocks produced under low temperature conditions.

Greenstone

A field term for metamorphosed mafic and ultramafic igneous rocks.

Hematite

An oxide of iron.

Hydromorphic dispersion

A process caused by the movement of water.
 

Hydrothermal

Pertaining to heated water, particularly of magmatic origin associated with the formation of mineral deposits or the alteration of rocks.

Igneous

Formed by solidification of hot mobile material termed magma.

Indicated Mineral Resource

An ‘Indicated Mineral Resource” is that part of a Mineral Resource for which tonnage, densities, shape, physical characteristics, grade and mineral content can be estimated with a reasonable level of confidence. It is based on exploration, sampling and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drillholes. The locations are too widely or inappropriately spaced to confirm geological and/or grade continuity but are spaced closely enough for continuity to be assumed.

Induced polarization (IP)

Electrical geophysical field technique, commonly used to detect disseminated mineralization or alteration within a rock mass.

Inferred Mineral Resource

An ‘Inferred Mineral Resource” is that part of a Mineral Resource for which tonnage, grade and mineral content can be estimated with a low level of confidence. It is inferred from geological evidence and assumed but not verified from geological and/or grade continuity. It is based on information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drillholes which may be limited or of uncertain quality and reliability.

Intercepts

Distances between defined points.

Intrusion

A body of igneous rock that invades older rocks.

JORC Code

Australasian Code for Reporting of Mineral Resources and Ore Reserves.

Lanthanum

A soft, malleable metallic rare earth element.

Laterite

A strongly leached iron and aluminium rich rock, formed at the surface by weathering in tropical conditions.

Lava

Fluid rock such as that which issues from a volcano or fissure in the earth's surface.

Lead

A soft, heavy and malleable metal with a symbol of Pb.

Lithology

Composition and texture of rock.

Lode

Metalliferous ore that fills a fissure in a rock or a vein of ore deposited between layers of rock.

Mafic

Descriptive of rocks composed dominantly of magnesium and iron forming silicates.

Magnetite

A magnetic oxide of iron, Fe3O4.

Manganese

A hard brittle metallic element.

Massive sulphide

A mass of rock consisting of greater than 40% sulphides.

Measured Mineral Resource

A ‘Measured Mineral Resource’ is that part of a Mineral Resource for which tonnage, densities, shape, physical characteristics, grade and mineral content can be estimated with a high level of confidence. It is based on detailed and reliable exploration, sampling and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drillholes. The locations are spaced closely enough to confirm geological and/or grade continuity.

Metamorphism

The mineralogical, structural and chemical changes induced within solid rocks through the actions of heat, pressure or the introduction of new chemicals.

Metamorphic Grade

Classified by mineral assemblage based on the appearance of key minerals that were in equilibrium under a specific range of pressure and temperature.

Metasediment

Partly metamorphosed sedimentary rocks.

Mica

A mineral group , consisting of phyllosilicates with sheet-like structures.

Mineralization

The concentration of metals and their chemical compounds within a body of rock.

Molybdenum

A heavy hard silver-grey metallic chemical element.

Muscovite

A mineral member of the mica group containing potassium and aluminium.

Nickel

Silvery white metal that has the symbol Ni.

Ore

Mineral bearing rock that may be mined and treated at a profit.

Orogen

Belt of deformed rocks usually accompanied by intrusive rocks.

Outcrop

An exposure of bedrock at the surface.

Oxidation

Near surface decomposition by exposure to the atmosphere and ground water.

PGE

Platinum group elements.

ppb

Parts per billion (1000 million).

ppm

Parts per million.

Paleo

Relating to the past, ancient or fossil.

Pathfinder

Minerals used as to indicate the presence of a hidden body.

Pegmatite

Coarse grained igneous rock found usually as dykes associated with a large mass of plutonic rock.

Petrography/Petrology

The branch of science treating the systematic description and classification of rocks.

Platinum Group Elements (PGE)

A group of dense metallic elements, including palladium, platinum, osmium, iridium, and rhodium.

Porphyry

A rock with conspicuous crystals in a fine grained ground mass.

Proterozoic

Geological period approximately 570 to 2,400 million years ago.

Prospect

Area with anomalous exploration results.

Pyrite

An iron sulphide mineral.

Pyroxene

Silicate mineral common in basic rocks containing varying amounts of Ca, Na, Mg and Fe.

Pyrrhotite

A iron sulphide mineral found in basic igneous rocks, pegmatites and contact metamorphic deposits.

Quartz

A mineral composed of silicon dioxide.

RAB drilling

A drilling technique in which the cuttings are recovered outside the drill rods.

Rare earths

Oxides of a series of metals with atomic numbers 57 to 71, which are widely distributed but relatively scarce minerals.

Reconnaissance

A general examination or survey of a region with reference to its main features.

Regolith

The loose, incoherent mantle of rock fragments, soil, wind blown sand, alluvium etc. which rests upon solid rock.

Reserve

In-situ mineral occurrence which has had mining parameters applied to it from which valuable or useful minerals may be recovered.

Resource

In-situ mineral occurrence from which valuable or useful minerals may be recovered.

Reverse circulation (RC) drilling

A drilling technique in which the cuttings are recovered through the drill rods thus minimizing sample losses and contamination.

Rock chip sampling

The collection of representative samples of rock fragments within a limited area.

Rotary air blast (RAB) drilling

Rotary drilling technique in which sample is returned to surface outside the rod string by compressed air.

Sandstone

A cemented or otherwise compacted detrital sediment composed predominantly of quartz grains.

Schist

A metamorphic rock with a platy or foliated texture.

Secondary

Formed as consequence of alteration of pre-existing minerals.

Sediment

Rocks formed by the deposition of solids from water.

Sedimentation

The process of eroding, transporting material and its deposition to form a rock.

Selenium

A rare non-metallic chemical element.

Sericite

A fine grained version of muscovite mica.

Shale

A laminated sedimentary rock formed by the consolidation of mud or silt.

Shear

A fracture in rock similar to a fault.

Silica

Silicon dioxide, SiO2.

Silicate

A compound whose crystal lattice contains silica tetrahedra through joining one or more groups of structures.

Siltstone

A very fine grained consolidated clastic rock composed predominantly of silt grade.

Soil sampling/geochemistry

The determination of relative or absolute abundances of elements and compounds in soil.

SQL database

Structured query language used to create, modify and retrieve data from relational database management systems.

Stockwork

A network of, usually quartz veinlets diffused in the original rock.

Stratigraphy

Composition, sequence and correlation of stratified rock in the earth's crust.

Stringer zone

A complex system of structurally controlled or randomly orientated veins.

Structural

Pertaining to geological structure.

Strike

The course or bearing of a bed or layer of rock.

Sulphide

A mineral compound characterized by the linkage of sulphur and metal.

Supergene

Typical supergene processes are solution, hydration, oxidation, deposition from solution and reactions of ions in solution with ions in existing minerals.

Syncline

A fold in rock strata that is concave upwards with a core of younger rocks.

Synform

Similar geometric shape as a syncline.

Tantalum

A hard blue grey metal that has the symbol Ta.

Tertiary

The earlier of two geologic periods comprising the Cenozoic era.

Tectonic

Of, pertaining to, or designating the rock structure and external forms resulting from the deformation of the earth's crust.

Terrane

A crustal block that preserves a distinctive geologic history that is different from the surrounding areas and that is usually bound by faults.

Thrust

A reverse fault characterised by a low angle of inclination.

Tin

Silvery metal that has the symbol Sn, obtained chiefly from the mineral cassiterite.

Tuff

A rock formed of compacted volcanic fragments, generally less than 4mm in diameter.

TURAM

A ground based electromagnetic technique.

Ultramafic

Descriptive of igneous rock containing virtually no quartz or feldspar and composed essentially of iron and magnesian silicates, mainly olivine and pyroxene.

Unconformity

A surface of erosion or non-deposition that separates younger strata from older rocks.

Uranium

A white radioactive metallic chemical element.

Vein

A thin sheet-like intrusion into a fissure or crack, commonly bearing quartz.

Volcanic

Descriptive of rocks originating from volcanic activity.

Volcaniclastic

Pertaining to clastic rock containing volcanic material.

Volcanogenic

Formed by processes directly connected with volcanism.

Volcanogenic massive sulphide deposit

Are a type of metal sulphide ore deposit, mainly Cu-Zn which are associated with and created by volcanic associated hydrothermal events (VHMS).

Weathering

The group of processes that change the character and composition of rocks by decay.

Zinc

A bluish white metal that has the symbol Zn.