| facies | | characteristic of a sediment as having been deposited in a particular environment |
| family | | part of the taxonomic hierarchy |
| fault (1) | | a major fracture in the Earth's crust |
| fault (2) | | fracture in rock caused by displacement |
| feldspar | | common igneous mineral containing silicon, aluminium and oxygen - one of the main components of granite |
| felsic | | rocks composed mainly of quartz and feldspar |
| ferberite | | iron manganese tungstate |
| fergusonite | | yttrium niobium oxide mineral |
| ferroaxinite | | hydrous calcium iron magnesium borosilicate mineral |
| ferromagnetic | | mineral strongly attracted to a magnet |
| fiamme | | fragments of flattened pumice found in ignimbrites |
| fissility | | property of a rock or mineral that breaks into thin flat parallel sheets |
| fissure | | a vertical crack in a rock body |
| flashflood | | rare violent flooding found in desert environments |
| flint | | silicon oxide mineral |
| floodplain | | flat land either side of a river |
| fluidal | | texture formed by flow motion seen in crystals within lavas |
| fluorescence | | photoluminescence under ultra-violet light |
| fluorite | | calcium fluoride |
| fluorspar | | see fluorite |
| fluting | | infilled scour marks on the bedding plane of a turbidity deposit |
| fluvial | | relating to a river |
| fluvioglacial | | deposits derived from the meltwaters of glaciers |
| focus | | the point of origin of an earthquake, usually along a fault plane |
| fold | | distortion produced by compression or shear through tectonic action |
| foliated | | mineral aggregates that flake easily |
| foliation | | parallel alignment of mineral plates such as mica |
| foraminifera | | single celled minute marine organisms |
| fore-arc | | in-filled basin formed above a subduction zone |
| foreshocks | | seismic tremors occurring prior to a major earthquake |
| form | | the shape and physical characteristics of a crystal |
| formation | | unit of rock distinct from those rocks above and below it |
| fossil | | remains of an organism preserved in the rocks |
| fractionation | | the process of change within a magma that leads to the formation of different rock types - see comagmatic |
| fracture | | the manner in which a rock or mineral breaks |
| franklinite | | zinc manganese iron oxide mineral |
| fuchsite | | hydrous potassium aluminium silicate mineral |
| fulgurite | | irregular pipe shaped rock formed by lightening strike melting country rocks |
| fumarole | | gas vent from an active volcano |
| funnel | | in cephalopods the pliable structure through which water is pumped to produce propulsion |
| gabbro | | coarse grained intrusive igneous rock similar chemically to basalt |
| gadolinite | | beryllium iron yttrium silicate mineral |
| galena | | lead sulphide mineral |
| gangue | | the waste rock left behind after mineral extraction |
| garnet | | silicate mineral crytalline gemstone found in metamorphic rocks |
| garnierite | | hydrous nickel magnesium silicate mineral |
| gastropods | | a class or molluscs, both marine and land, usually possessing a coiled shell |
| gault | | clay found at the base of Cretaceous strata |
| gehlenite | | calcium magnesium aluminium silicate mineral |
| gel | | a semisolid colloidal solution |
| gemmology | | the study of gemstones |
| genus | | part of the taxonomic hierarchy |
| geode | | cavity in the centre of a rock lined with crystals |
| geology | | study of the Earth, how it was formed, natural processes at work etc |
| geosuture | | contact between two rock masses such as adjacent continental plates |
| geyser | | thermal emission of water from underground springs, produced by volcanic action |
| gipsy | | see bourne |
| glabella | | axial portion of the head of a trilobite |
| glaciation | | period where ice advances from the poles |
| glauberite | | sodium calcium sulphate mineral |
| glaucodot | | cobalt iron arsenic sulphide mineral |
| glauconite | | hydrous potassium aluminium iron magnesium silicate mineral |
| glaucophane | | hydrous sodium magnesium aluminium silicate mineral |
| gneiss | | coarse grained metamorphic rock |
| goethite | | iron hydroxide mineral |
| gondwanaland | | "supercontinent" that existed in the southern hemisphere during the Palaeozoic and early Mesozoic eras |
| goniometer | | instrument for measuring the angles between the faces of a crystal |
| gossan | | strata immediately below the Earth's surface |
| graben | | narrow strip of land that has sunk between two parallel faults |
| granite | | speckly coarse grained igneous rock containing quartz and feldspar |
| granoblastic | | uniform texture seen in a metamorphic rock where the crystals are all of similar size |
| granoclastic | | uniform texture seen in rock altered through tectonic processes |
| granodiorite | | igneous rock of intermediate composition |
| granophyre | | medium grained granite rock with interlocking crystals of feldspar and quartz |
| granophyric | | texture of a rock comprising irregularly sized and shaped crystals |
| granulite | | orthoclase/plagioclase metamorphic rock |
| graphite | | softest allotrope of carbon |
| graptolite | | extinct colonial animals |
| gravity (specific) | | difference between a rocks weight and the weight of an equivalent volume of water |
| greenockite | | cadmium sulphide |
| greensand | | sandy deposits containing glauconite |
| greisen | | igneous rock altered by contact with volatile fluids |
| greywacke | | conglomerate containing grain sizes between clay particles and pebbles |
| griquaite | | intrusive igneous rock |
| grit | | term used for carboniferous limestones whose texture made them ideal for use as mill-stones |
| grossular | | calcium aluminium silicate mineral |
| groundmass | | fine grained matrix in an igneous rock |
| group | | two or more adjacent rock formations |
| grykes | | joints in a limestone pavement |
| guard | | see rostrum |
| guyot | | flat topped seamount (undersea volcano) |
| gymnosperm | | a seed plant carrying the ovules on cone scales rather than enclosed in an ovary |
| gypsum | | hydrated calcium sulphate mineral |
| habit | | the shape and physical characteristics of a crystal |
| hachuring | | shading on a topographical map to show reliefs |
| hade | | incline in degress of a fault plane |
| haematite | | iron oxide mineral |
| halides | | family name for the chlorides, bromides, fluorides and iodides |
| halite | | sodium chloride mineral (rock salt) |
| hanging valley | | valley formed by a river that enters a deeper valley produced by glaciation |
| hardness | | the resistance of a mineral to scratching - see Moh's Scale |
| harmotome | | hydrated barium potassium aluminium silicate mineral |
| hassock | | a soft sandy limestone |
| hauerite | | manganese sulphide mineral |
| hausmannite | | manganese oxide mineral |
| hauyne | | sodium calcium aluminium silicate mineral sulphate mineral |
| head shield | | part of a trilobite that covered the animals head |
| heave | | sideways movement along a fault plane |
| heavy | | minerals with a specific gravity greater than 2.9 |
| hedenbergite | | calcium iron silicate mineral |
| heliotrope | | silicon oxide mineral |
| hemihedral | | crystalline structure that displays minimal symmetry |
| hemimorphite | | hydrated zinc silicate mineral |
| herderite | | calcium beryllium phosphate mineral |
| heterotroph | | an organism that obtains carbon from the organic matter it ingests |
| heubnerite | | iron manganese tungstate mineral |
| heulandite | | hydrated sodium calcium aluminium silicate mineral |
| hogsback | | single sloped monocline structure |
| holdfast | | root-like structure in crinoids that attached the animal to the sea floor |
| holocene | | most recent geological era representing the last 10,000 years |
| holocrystalline | | rock formed entirely of crystals |
| holohedral | | crystalline structure that displays perfect symmetry |
| hominid | | any animal resembling man |
| homology | | similarities in different animals due to common ancestry |
| horn | | steep jagged mountain peak produced through glaciation |
| hornblende | | complex silicate mineral |
| hornfels | | fine grained glassy rock produced through contact metamorphism |
| hornstone | | silicified (fossil) wood |
| horst | | upraised block of land between two faults |
| hot spot | | isolated region of the Earth's mantle hot enough to melt the rock strata above it |
| hoxnian | | interglacial period from c. 380,000 - 320,000 years ago |
| hyaline | | texture of a glassy substance |
| hyaloclastic | | texture of rocks formed by rapid cooling of glassy fragments emitted by volcanic action |
| hyaloclastitite | | type of basalt |
| hyalopilitic | | volcanic rocks composed of glass (obsidian) accompanied by crystals of feldspar |
| hybrid | | rock derived from a mixture of different magmas |
| hydromagnesite | | hydrated magnesium carbonate mineral |
| hydrosphere | | the water that exists on earth in the atmosphere, lakes, seas etc |
| hydrothermal | | hot water produced by volcanic action |
| hydrozincite | | hydrous zinc carbonate mineral |
| hygroscopic | | substance that attracts water |
| hypabyssal | | forming deep in the Earth's crust |
| hypidiomorphic | | texture of a rock comprising both euhedral and anhedral minerals |
| hyposilicic | | rock containing less than 50% silicon - see mafic |
