| cabochon | | convex cut stone or gem with one flat side |
| cainozoic | | see cenozoic |
| cairngorm | | silicon oxide mineral |
| calcareous | | containing calcium carbonate mineral |
| calciphyre | | calcite/silicate metamorphic rock |
| calcite | | calcium carbonate mineral |
| caldera | | large circular depression associated with a volcano |
| callus | | thickened ridge of shell around the aperture of a gastropod |
| cambering | | breakup of rock strata due to bulging of underlying clay deposits |
| cancrinite | | complex silicate mineral |
| cannel | | intermediate type of coal between lignite and bituminous |
| carbonatite | | igneous rock that can be intrusive or extrusive |
| carnallite | | hydrated potassium magnesium chloride mineral |
| carnelian | | silicon oxide mineral |
| carnotite | | hydrated potassium uranium vanadate mineral |
| cartography | | science of producing maps |
| cassiterite | | tin oxide mineral |
| cast | | fossil representation of a dead organism where the original skeleton has dissolved and been replaced by ano |
| cataclasis | | process during tectonic movements where rocks are pulverised |
| cataclastic | | texture of rocks deformed by tectonic action, such as breccia |
| caudal | | relating to the tail |
| CCD | | carbonate mineral compensation depth - depth in seawater at which calcium dissolves |
| celestite | | strontium sulphate mineral |
| cementation | | the process whereby sedimentary grains aggregate into a rock stratum |
| cenozoic | | era covering the period from 65 million years to present |
| cephalic | | relating to the head |
| cephalopod | | a class of marine molluscs that includes squids, octopuses etc |
| cerussite | | lead carbonate mineral |
| chabazite | | hydrated calcium aluminium silicate mineral |
| chalcanthite | | hydrated copper sulphate mineral |
| chalcedony | | silicon oxide mineral |
| chalcocite | | copper sulphide |
| chalcopyrite | | copper iron sulphide |
| chalk | | fine grained limestone comprised of microscopic marine organisms |
| chalybeate | | water containing iron |
| channel-lag (deposits) | | coarse gravels laid down on the outside of a river bend |
| chela | | a claw |
| chernozem | | rich well developed soils found in grasslands |
| chert | | silicon oxide mineral |
| chine | | ravine found along eroding coastlines |
| chlorargyrite | | silver chloride mineral |
| chlorite | | pale green micaceous mineral |
| chloritoid | | hydrous iron magnesium aluminium silicate mineral |
| chondrite | | stony meteorite containing chondrules |
| chondrite (carbonaceous) | | chondrite containing a high proportion of carbon |
| chondrodite | | hydrous magnesium iron silicate mineral |
| chondrules | | globular shaped mineral aggregate found in some meteorites |
| christobalite | | silicon oxide mineral |
| chromite | | iron chromium oxide mineral |
| chrysoberyl | | beryllium aluminium oxide mineral |
| chrysocolla | | hydrous copper silicate mineral |
| chrysoprase | | silicon oxide mineral |
| chrysotile | | hydrous magnesium silicate mineral |
| cilia | | minute hair-like structures on some marine organisms |
| cinnabar | | mercury sulphide |
| cirque | | small ice filled basin formed by glacial "plucking" |
| cirrus | | articulate appendage of a crinoid |
| citrine | | silicon oxide mineral |
| cladogram | | diagram showing sequences in an evolutionary tree |
| class | | part of the taxonomic hierarchy |
| clast (1) | | splinter formed by fragmentation through transportation, vulcanism or meteoric impact |
| clast (2) | | particle within a sedimentary rock |
| clay | | aluminium magnesium silicate mineral deposit formed from the decay of rocks such as feldspar |
| cleavage | | tendency of minerals to split along particular planes |
| clinochlore | | hydrous magnesium iron aluminium silicate mineral |
| clinometer | | instrument for measuring angles from the horizontal used for measuring dip |
| clinozoisite | | hydrous calcium aluminium silicate mineral |
| clints | | weathered limestone blocks along a bedding plane |
| cnidaria | | phylum containing corals |
| cobaltite | | cobalt arsenic sulphide mineral |
| coccoliths | | microscopic calcareous remains of single celled algae, the major component of chalk |
| colemanite | | hydrated calcium borate mineral |
| colloform | | kidney shaped masses produced by colloidal precipitation |
| colloid | | liquid containing a suspension of very fine particles |
| colony | | connected group of polyps |
| columbianite | | pink meteoric glass |
| columbite | | iron manganese niobium tantalum oxide mineral |
| columella | | central support structure in a gastropod shell |
| columnar | | rod like |
| comagmatic | | different igneous rock types derived from the same magma |
| compaction (1) | | packing of sedimentary grains by the weight of overlying strata |
| compaction (2) | | formation of a sedimentary rock under pressure |
| competence | | banded rocks that break rather than flow when under stress |
| complex | | a grouping of different rock types found in the same area |
| composite (volcano) | | volcanic cone built up by alternating pyroclastic flows and lava streams |
| compression (pulse) | | time taken by a rock to transmit a seismic P-wave |
| conchoidal | | smooth fracture in a rock such as obsidian, flint etc |
| concordant | | igneous intrusion that does not cut across country rock strata |
| concretion | | authigenic mineral growth around a nucleus |
| conglomerate | | very coarse grained sedimentary rock containing pebbles |
| conichalcite | | hydrous calcium copper arsenide mineral |
| conodont | | small fossil teeth from fish like animals |
| constructive (margin) | | tectonic boundary where crust is being formed |
| continental drift | | the movement of tectonic plates |
| contours | | lines on a physical map joining points of equal height |
| coombe (rock) | | type of rock found in the lower chalk |
| copiapite | | hydrated iron sulphide |
| coprolite | | fossilised excrement |
| coquina | | rock composed mainly of shell fragments |
| corallite | | skeleton of an individual coral polyp |
| cordierite | | magnesium aluminium silicate mineral |
| core | | central part of the Earth beneath 3000km |
| correlation | | comparison of rock strata to determine relative ages |
| corrie | | see cirque |
| corundum | | aluminium oxide mineral |
| country (rocks) | | "native" rocks that have been intruded into and/or surrounded by a plutonic igneous intrusion |
| covellite | | copper sulphide |
| crag | | term applied to Tertiary rocks from the Pliocene and Pleistocene |
| crater | | circular depression formed by meteoric impact or on a volcano |
| craton | | stable continental basement rocks, usually Pre-Cambrian |
| crawfordjohn | | see essexite |
| creep | | gradual movement of rocks under stress |
| crinoid | | "sea lily", marine echinoderm attached to the sea floor |
| crinoidea | | class of echinoderms |
| crocoite | | lead chromate |
| cromerian | | interglacial period from c. 580,000 - 540,000 years ago |
| cross-bedding | | inclined beds between bedding planes |
| crust | | the thin outermost layer of the Earth |
| cryolite | | sodium aluminium fluoride |
| crystal | | geometric form determined by the arrangement of its constituent atoms |
| cummingtonite | | hydrous magnesium silicate mineral |
| cumulate | | igneous rock formed by the settling of crystals within a large mafic igneous body |
| cuprite | | copper oxide mineral |
| curie (temperature) | | temperature at which a mineral loses its inherent magnetism |
| cwm | | see cirque |
| cyanobacteria | | blue-green algae that form stromatolites |
| cyanotrichite | | hydrated copper aluminium sulphate mineral |
| cyclothem | | repeating rock types in cycles |
| dacite | | volcanic type of granodiorite |
| danburite | | calcium borosilicate mineral |
| datolite | | hydrous calcium borosilicate mineral |
| decrepitation | | the breaking apart of a rock or mineral due to expansion through moisture absorbtion, decay etc |
| deformation | | rock features resulting from faults, folds etc |
| delta | | multiple estuaries where a river meets the sea |
| delta (arcuate) | | microtidal area where sediment is deposited in a sandbar formation |
| delta-bar | | region where much of a rivers bedload is deposited |
| deltaic | | pertaining to a river delta |
| delthyrium | | aperture from which the pedicle emerges on a brachiopod |
| dendrite | | skeletal crystals found found on the fracture surface of a rock |
| denehole | | shallow man-made pit remaining after small scale chalk or flint extraction |
| density | | the mass of a substance per unit volume |
| denudation | | weathering and erosion of mountains |
| descloizite | | hydrous lead zinc vanadate |
| desert | | region where rainfall is less than 150mm per annum |
| detrital (grains) | | minerals eroded out of its original parent rock and redeposited as a new sediment |
| detritus | | dead organic matter |
| devensian | | glacial period from c. 70,000 - 10,000 years ago |
| dextral | | fault in which rocks are moved to the right |
| diabase | | hypabyssal igneous rock |
| diablastic | | texture of a metamorphic rock consisting of acicular or fibrous minerals oriented in the same direction |
| diachronous | | jumbled sedimentation along a bedding plane where the sediments are not all of the same age |
| diagenesis | | process of consolidation that transforms a sediment into a sedimentary rock |
| diamagnetic | | mineral weakly repelled by a magnet |
| diamond | | hardest form of carbon |
| diapir | | body of magma (or salt) that rises through the crust due to it being lighter than the surrounding rocks |
| diaplectic | | substance (usually glassy) derived by impact metamorphism |
| diapsid | | reptile type where the skull contains openings in the temple region i.e lizards, snakes, crocodiles |
| diaspore | | aluminium hydroxide mineral |
| diatom | | microscopic plant remains |
| dichroism | | two different colours exhibited by a mineral depending on the plane viewed |
| differentiation | | the process of change within a magma that leads to the formation of different rock types - see comagmatic |
| dimorphism | | two distinct types of the same species, i.e male & female |
| diopside | | calcium magnesium silicate mineral |
| dioptase | | hydrous copper silicate mineral |
| diorite | | igneous rock of intermediate composition |
| dip | | angle of a bedding plane to the horizontal - see strike |
| dislocation | | intersection of a fault or fracture with the Earth's surface |
| distal (1) | | sediments laid down farthest from their point of origin |
| distal (2) | | perpedicular to the axis of a body |
| dog-tooth-spar | | see calcite |
| dolerite | | medium grained basic rock |
| dolomite | | calcium magnesium carbonate mineral |
| dome | | the upper structure of an intrusive igneous body |
| dorsal | | usually the back of an animal |
| downthrow | | vertical displacement along a normal fault |
| dreikanter | | three sided pebble that has been eroded in a desert environment by wind |
| drift | | collective term for deposits of Quaternary age |
| drift (longshore) | | the gradual movement of beach deposits along a coastline due to tidal action |
| dripstone | | smooth calcite deposits found in caves formed by evaporation of saturated water |
| drowned (valleys) | | valley formed by river or glacial action now linked to the sea |
| drumlin | | low boulder clay hill formed beneath a glacier |
| druse | | fine crystals coating a rock or lining a cavity |
| dry-valley | | valley formed by river or glacial action where the river or glacier has disappeared |
| dumortierite | | aluminium borosilicate mineral |
| dune (aeolian) | | large sand hill formed by wind blown sand |
| dune (seif) | | ridge of sand formed parallel to the prevailing wind |
| dune (stellate) | | hill of sand with radiating ridges |
| dune (transverse) | | ridge of sand formed perpendicular to the prevailing wind |
| dunite | | intrusive igneous rock |
| dyke | | igneous material intruded into a fracture in "country" rocks |
| earthquake | | motion along fault planes or tectonic plates resulting in the release of energy |
| echinodermata | | phylum of marine animals comprising sets of interlocking plates (sea urchins) |
| echinoid | | marine sea urchin |
| eclogite | | anhydrous rock formed of pyroxene and garnet |
| ediacara | | South Australian location famous for its Precambrian fossil fauna |
| efflorescence | | migration of salts from the interior of a geological specimen due to fluctuating humidity |
| effusive | | the slow production of lava from a volcano |
| ejecta | | material thrown out of a crater by meteoric impact |
| embrechite | | see migmatite |
| emerald | | green gemstone form of beryl |
| enargite | | copper arsenic sulphide mineral |
| endemic | | species found only in a particular area |
| endoskeleton | | internal skeleton of an animal |
| enstatite | | magnesium silicate mineral |
| eon | | largest unit of geological time, see archaeozoic, proterozoic, phanerozoic |
| eosphorite | | hydrated manganese aluminium phosphate mineral |
| epeirogenic | | changes in local sea level due to isostatic movements |
| epicentre | | point on the surface of the Earth directly over the centre of an earthquake |
| epidote | | hydrous calcium aluminium iron silicate mineral |
| epifauna | | animals that live on or above the seafloor |
| epiplutonic | | igneous rock that has crystallised at intermediate depth in the Earth's crust |
| epitaxy | | two crystals of different minerals growing on or around each other |
| epsomite | | hydrated magnesium sulphate mineral |
| equigranular | | texture where all individual mineral grains are approximately the same size |
| erg | | wide shallow basin in a deep desert environment |
| erratics | | "foreign" rocks transported by glacial action, not usually associated with the place of discovery |
| erythrite | | hydrated cobalt arsenate mineral |
| esker | | long sand/gravel ridge produced underneath a glacier by meltwaters |
| essential | | a substance that is an acknowledged major component of a rock type |
| essexite | | igneous rock sometimes found as xenoliths |
| euclase | | hydrous beryllium aluminium silicate mineral |
| euhedral | | crystals that display their usual form |
| eurypterid | | extinct marine arthropod, known as the "sea scorpion" |
| eustatic | | world wide changes in sea level associated with changes in the polar icecaps |
| evaporite | | sedimentary rock formed by the evaporation of a solution, i.e. Halite (rock salt) |
| exfoliation | | peeling away of thin layers of rock by erosion |
| exoskeleton | | external skeleton of an animal, ie insects, crustacea |
| exposure | | exposure of underlying rocks at the surface |
| extinction (mass) | | the wholesale destruction of many living plants and animals at the same time |
| extrusive | | a rock formed by the crystallisation of magma on the Earth's surface (opposite of intrusive) |
| ezoic | | old term for the Archaean era |
