glossary of terms, phrases, symbols and abbreviations used on this site


A
Amphibolite: A metamorphic rock consisting mainly (but not entirely) of amphibole, usually with an oriented rock fabric.
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B
Breccia: a group of rocks consisting of angular, poorly sorted fragments.
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C
Carbonates: materials of carbonate chemistry such as limestone (calcium carbonate CaCO₃)
: planes of weakness in the atomic lattice of a mineral, along which the mineral will preferentially split when struck.
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D
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E
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F
Field: geology studied in situ is said to be 'in the field'.
Fining sequence: a bed or sediment layer showing a gradational change of grain size.
Fossil: a trace of organic material which has been buried and permanently preserved by natural processes. A fossil may be a 'body' fossil; the preserved fossilized remains of an organism's skeleton or, more rarely, flesh; or a 'trace' fossil; preserved evidence of the presence of an organism such as an impression, tracks, borings or excremental material.
Fossil fuel: a hydrocarbon deposit which may be used as a fuel. e.g.. coal, oil, natural gas.
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G
Gabbro: a coarse grained, basic (low in SiO₂) plutonic (deep intrusive) igneous rock, often olivine-bearing.
Geologist: a person who specializes in the geological sciences.
Geology, geological sciences: the study of the Earth and it's processes, structure, composition and history. Geology incorporates the following branches: (1) concerning the composition of the Earth; crystallography, geochemistry, mineralogy, petrology. (2) concerning the structure of the Earth; structural geology, geophysics. (3) concerning the history of the Earth; stratigraphy, historical geology. (4) concerning the evolution of life on Earth; palaeontology. (5) concerning the physical processes affecting the Earth; physical geology.
Gneiss: A name applied to a broad group of rocks. Generally speaking gneisses are banded rocks formed during high-grade regional metamorphism
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H
Hydrocarbons: substances composed of hydrogen and carbon such as oil, coal and natural gas.

I
Igneous: a rock derived from fresh melt material (primary source material). i.e.. those rocks formed at volcanoes as lava flows and those injected into the crust such as granites.

J
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K
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L
Lustre: the appearance of a mineral due to the amount and quality of light reflected by it's surfaces. e.g.. vitreous.
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M
Ma: abbreviation for mega-annum, meaning 10⁶ (one million) years.
Metallic: a term used to describe the lustre of the 'metallic' minerals.
Metamorphic: a rock (sedimentary, igneous or metamorphic) which has undergone alteration by extreme heat and/or pressure thereby altering it's physical properties.
Moho: an abbreviation for the Mohorovicic Discontinuity.
Mohorovicic Discontinuity: the zone which separates the crust from the mantle. Average depth 35km. Usually seismically defined.

Mineral: a naturally occurring chemical compound (or element) of known physical properties (which may vary within fixed limits). Minerals are usually solid, although some may be liquid (e.g.. mercury) or gaseous (e.g.. natural gas). Minerals and are usually inorganic, although some are of organic origin (e.g.. Amber, Chalk, Oil). Most minerals may exist in three states under different pressure/temperature conditions.
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N
Native element: a single chemical element occurring naturally as a mineral e.g.. gold.
Non-metallic: the non-metallic minerals, which have lustres other than metallic, e.g. the vitreous minerals.
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O
Olivine: a mineral and gemstone.
Olivine gabbro: An olivine-bearing gabbro
Oligoclase: a variety of feldspar, a non-metallic mineral.
Ordovician: Period from 500 Ma to 435 Ma
Organic: a substance of organic origin / composed of the organic elements (hydrocarbons) e.g.. amber, coal
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P
Peridotite: an ultrabasic (extremely low SiO₂) igneous rock, consisting almost entirely of olivine. Approximate composition of the upper mantle.
Plagioclase: a variety of feldspar, a non-metallic mineral.
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Q
Quartz: a common rock forming, non-metallic mineral.
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R
Rhombohedral: In the shape of a rhombohedron. The rhombohedral (trigonal) crystal system. Minerals may have a rhombohedral crystal form, or may have rhombohedral cleavage. Calcite is an example of a rhombohedral crystal with rhombohedral cleavage.
Rhyollite: fine grained, acid (rich in SiO₂) volcanicigneous rock.

Rock: a naturally formed substance consisting of one or more minerals.
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S

Scree: a mass of loose, coarse debris resulting from the weathering of rocks. Formed in situ or transported short distances by gravity to form a scree slope.
Sedimentary: a rock which originated as a sediment and has not undergone metamorphism, such as a mudstone, sandstone or chalk.
Serpentinite: a rock in which the mineral serpentine has replaced other minerals as an alteration product, usually do to hydrothermal actions in the late stages of the rocks formation.
Silicates: materials of silicate chemistry (those based on silica SiO₂) such as feldspar, biotite, beryl.
Spoil: the waste product of a mining or quarrying process. Spoil heap, spoil tip.
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T
Tuffs: a type of pyroclastic rock, that is; one which has been violently ejected from a volcano.
Turbidity sequence: a sequence of sediment layers (bedding) of varying coarseness (grain size) or containing other characteristic structures indicating deposition by a turbidity current.
Turbidity current: sediment in transport in sea water acting as a dense fluid.
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U
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V
Vitreous: a mineral with a 'glassy' lustre
Volcanic: associated with or the product of volcanoes, or all extruded igneous rocks.
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W
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X
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Y
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Z
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[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Y] [Z]
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