| amygdale amygdule | a filled, commonly almond-shaped, vesicle in rock. |
| andesite andesyte | a fine-grained volcanic rock of intermediate composition, consisting largely of PLAGIOCLASE and one or more mafic minerals. |
| andesitic | of or like ANDESITE, a fine-grained volcanic rock. |
| aphanite | any rock of such close texture that separate minerals contained within it cannot be distinguished by the naked eye. |
| aphanitic | of igneous rocks, fine-grained. |
| aplite haplite | a fine-grained, light-coloured igneous rock. |
| aplitic | of or like APLITE, a fine-grained, light-coloured igneous rock. |
| arenite | a rock made up chiefly of sandy grains. |
| arenitic | of or like ARENITE, a rock made up chiefly of sandy grains. |
| arkose | a sedimentary rock formed by the cementation of sand-sized grains of feldspar and quartz. |
| arkosic | pertaining to ARKOSE, a type of sandstone. |
| banket | a gold-bearing pebbly conglomerate. |
| basalt | a highly mafic igneous volcanic rock, typically fine-grained and dark in color. |
| basaltic | of or like BASALT. |
| batholite batholith bathylite bathylith | a mass of igneous rock that has risen from a great depth. |
| bauxite beauxite | an earthy rock consisting of hydrated alumina with variable proportions of iron oxides and other impurities. |
| bauxitic | of or like BAUXITE, a rock composed of aluminum hydroxides and impurities in the form of silica, clay, silt, and iron hydroxides. |
| bedrock | general term referring to the rock underlying other unconsolidated material, i.e. soil. |
| bioclastic | derived from shell fragments or similar organic remains. |
| biostrome | a rock layer consisting of a deposit of organic material such as fossils. |
| boulder | a large rock. |
| bouldery | full of boulders. |
| brash | a collection of broken pieces of rock or ice; (verb) to attack > BRASHED, BRASHING; (adj.) forward, over-confident > BRASHER, BRASHEST. |
| brashy | like BRASH > BRASHIER, BRASHIEST. |
| breccia | a geological formation consisting of angular fragments of rock. |
| breccial | of or like BRECCIA, a geological formation consisting of angular fragments of rock. |
| brecciate | of a rock, composed of angular fragments; (verb) to break a rock down into angular fragments. |
| brocatel brocatelle | a type of variegated marble from France or Italy. |
| brockram | breccia. |
| brownstone | a dark variety of SANDSTONE, much used for building purposes. |
| buhr | a variety of quartz. Cf. BUHRSTONE. |
| buhrstone burrstone burstone | a cellular, flinty rock, used for mill stones. |
| calcrete | a composite rock of sand and gravel cemented with calcium carbonate. |
| calcsinter | another name for TRAVERTINE, a pale limestone deposited from solution. |
| calctufa | a rock made of fine volcanic detritus. See also TUFA, TOPH, TOPHE. |
| calctuff | a general term for all consolidated pyroclastic rock. See also TUFF. |
| caliche | gravel, sand, or desert debris cemented by calcium carbonate, an accumulated product of chemical weathering in a dry climate. |
| calmstonecamstanecamstone caumstone | a white argillaceous stone used for whitening doorsteps. |
| calp | in Ireland, a dark shaly limestone. |
| caprock | an overlying rock layer. |
| chondre chondrule | a spheroidal mineral grain embedded in a meteorite. [Gk. chondros a grain, grit, cartilage]. |
| chondrite | a meteoric stone characterized by the presence of CHONDRULES. |
| ciminite | a rock intermediate between TRACHYTE and ANDESITE. |
| clarain | lustrous, brightly coloured bands in coal. |
| clast | an individual grain or constituent of a rock. |
| clastic | a rock composed of other rocks. |
| claystone | a compact very fine-grained rock consisting of consolidated clay particles. |
| coal | a carbonaceous rock; (verb) to dig for coal; to transport coal. |
| coalball | a calcareous nodule found in coal. |
| colluvium | material which accumulates at the foot of a steep slope. Pl. COLLUVIA or COLLUVIUMS. |
| coquina | a coarse-grained, porous variety of clastic limestone made up chiefly of shells and shell fragments. |
| coralloid | having the form of coral; branching like coral. |
| cornbrash | a clayey limestone whose presence in the soil affords good growth for cereal crops. |
| cornstone | a silicious limestone favourable for cereal crops. |
| dacite | a type of igneous volcanic rock. |
| devonian | relating to a type of rock formed in the fourth period of the Palaeozoic era. |
| diabase | rock that is, in essence, a fine-grained GABBRO. |
| diabasic | of or like DIABASE, a fine-grained GABBRO. |
| diapirism | the upward material of material through denser rock. |
| diatomite | a siliceous sedimentary rock formed from the accumulations of diatoms or other nanoplankton. |
| diedre | a rock angle or re-entrant corner, usu. with a crack in it. |
| diorite | a crystalline granular igneous rock composed of plagioclase and hornblende. |
| dioritic | containing DIORITE. |
| dolerite | a type of igneous rock. |
| doleritic | of the nature of DOLERITE; as, much lava is doleritic lava. |
| dolomite | a carbonate sedimentary rock, magnesian limestone. |
| dolomitic | pertaining to DOLOMITE, a carbonate sedimentary rock. |
| dropstone | a stone embedded in a sedimentary deposit and believed to have got there after being released from a melting glacier. |
| druse | a crust of small projecting crystals on a rock. |
| dunite | a type of igneous rock. |
| dunitic | relating to DUNITE, an igneous rock. |
| duricrust | gravel, sand, or desert debris cemented by calcium carbonate, an accumulated product of chemical weathering in a dry climate, aka CALICHE. |
| eaglestone | a hollow oval nodule of clay ironstone. |
| eclogite eklogite | a crystalline rock containing red garnet. |
| eluvial | relating to an ELUVIUM, an accumulation of rock debris. |
| eluviate | to subject (soil) to ELUVIATION. |
| eluvium | an accumulation of rock debris. Pl. ELUVIA or ELUVIUMS. |
| elvan | a kind of granite. [Welsh elfen, element]. |
| elvanite | the rock of an elvan vein, or the elvan vein itself; an elvan course. |
| eocene | of rock formed in the second epoch of the Tertiary geological period. |
| epidosite | a rock composed of EPIDOTE and quartz. |
| erathem | the stratigraphical unit of rock strata, corresponding to a geological era. |
| erratic | a boulder carried far from its origin by glacial action. |
| eucrite | a gabbroitic rock composed of lime-feldspar, pyroxenes and olivine. |
| eucritic | of or like EUCRITE, a gabbroitic rock. |
| eutaxite | a volcanic rock with a banded structure. |
| eutaxitic | of or like EUTAXITE, a volcanic rock with a banded structure. |
| evaporite | a sedimentary rock formed by the evaporation of salt water e.g. halite. |
| fahlband | in crystalline rocks, a stratum rich in metals. |
| faikes | thin-bedded shaly or micaceous sandstone. Also FAKES. |
| felsic felsitic | consisting of a fine patchy mosaic of quartz and feldspar. |
| felsite felstone | a fine-grained rock, flintlike in fracture, consisting essentially of orthoclase feldspar with occasional grains of quartz. |
| felstone | see FELSITE. |
| flaser | an irregular streaky lenticular structure developed in metamorphic rocks. |
| flintify | to turn into flint. |
| flysch | a great Alpine mass of Cretaceous and Lower Tertiary sandstone with shales. |
| footwall | the layer of rock beneath a vein of ore. |
| fulgurite | a vitrified sand tube produced by the striking of lightning on sand. |
| gabbro | a coarsely crystalline igneous rock composed of labradorite or similar plagioclase and pyroxene, often with olivine and magnetite. Pl. GABBROS. |
| gabbroic gabbroid | of or like GABBRO. |
| gangue | worthless rock in which valuable metals occur. |
| ganister gannister | a flint-like rock used for lining Bessemer converters and for surfacing roads. |
| geode | a roughly spherical stone, hollow or partially hollow, containing an accumulation of mineral matter. |
| geodic | relating to a GEODE. |
| geofact | a rock chipped naturally that looks like an artifact. |
| gibber | (Native Australian) a stone, a boulder; (verb) to make inarticulate noises. |
| gneiss | a foliated usu. coarse-grained metamorphic rock typically consisting of feldspar, quartz, and mica. |
| gneissic gneissitic | of or like GNEISS. |
| gneissoid | like GNEISS. |
| gneissose | having the structure of GNEISS. |
| gossan gozzan | decomposed rock, largely quartz impregnated with iron compounds, at the outcrop of a vein especially of metallic sulphides. |
| granite | a highly felsic igneous plutonic rock. |
| granitic | of or like granite. |
| granitise granitize | to make like granite. |
| granitoid | resembling granite in granular appearance; as, granitoid gneiss. |
| granulite | a whitish, granular rock, consisting of feldspar and quartz intimately mixed. |
| graywacke greywacke | any coarse-grained, usu. dark sandstone containing angular mineral and rock fragments in a fine-grained clayey matrix. |
| greensand | a kind of sandstone consisting largely of grains of quartz and glauconite; esp. (G-) as forming strata in the Cretaceous System in Southern England. |
| greisen | a rock composed of quartz and mica. |
| greystone | a grey volcanic rock. |
| greywether | a sandstone boulder of S. England, aka SARSEN. |
| gritstone | a type of coarse sandstone. |
| groundmass | fine grained porphyritic base of porphyritic rock containing phenocysts. |
| haplite | see APLITE. |
| haplitic | of or like HAPLITE, a fine-grained, light-coloured rock. |
| helictite | a distorted form of stalactite resembling a twig. |
| holystone | a sandstone material used to scrape ships' decks; (verb) to scrape a deck with holystone > HOLYSTONES, HOLYSTONING, HOLYSTONED. |
| hornfels | a compact type of rock composed of lime silicates. |
| hypogene | formed or occurring beneath the surface of the earth, as opposed to EPIGENE. |
| igneous | of rock, formed by cooling and consolidation of magma. |
| ignimbrite | a hard rock formed by fusion of the volcanic fragments and dust of a nuee ardente. |
| impactite | a rock, typically glassy (in some cases vesicular) and/or fine grained crystalline, produced where a meteor has collided with the earth. |
| inclusion | a fragment of older rock caught up in an igneous rock. |
| inlier | an older rock formation completely surrounded by newer strata. N.B. there is no verb INLIE*. |
| intrusive | an intrusive rock or mass. |
| jaspilite | a rock like JASPER > JASPILITES. |
| jet | a hard black variety of LIGNITE that takes a brilliant polish and is used for jewellery, ornaments, etc. |
| killas | clay slate. [A Cornish miners' term]. |
| kingle | a very hard rock esp. sandstone. |
| krans krantz kranz | a crown of rock on a mountain-top. [Dutch krans, a wreath]. |
| kreep | a basaltic lunar rock. |
| kunkar kunkur | a concretionary limestone in India. [Hindi kankar, stone]. |
| laccolite laccolith | a mass of igneous rock intruded between two sedimentary beds. |
| lenticle | a lenticular piece or mass of rock, a small lentil. |
| leucitic | containing the mineral LEUCITE, as, leucitic rocks. |
| lias | the lowest series of rocks of the Jurassic system > LIASES. |
| lignite | a brown carbonaceous sedimentary rock with woody texture that consists of accumulated layers of partially decomposed vegetation. |
| lignitic | containing LIGNITE; resembling, or of the nature of, lignite; as, lignitic clay. |
| limestone | a sedimentary rock composed mostly of the mineral calcite, CaCO3. |
| liparite | a quartzose TRACHYTE, aka RHYOLITE. |
| lithify | to petrify, convert to rock. |
| lithology | the study of rocks. |
| lithotome | a stone so formed by nature as to appear as if cut by art. |
| lopolith | a lens-shaped body of igneous rock. |
| lutite | any rock derived from clay or mud. Also PELITE. |
| mafic | a generally dark-colored igneous rock with significant amounts of one or more ferromagnesian minerals, or to a magma with significant amounts of iron and magnesium. |
| magma | molten or partially molten rock material. Pl. MAGMAS or MAGMATA. |
| magmatic | of or like MAGMA, molten or partially molten rock material. |
| magmatism | the production of MAGMA. |
| marble | a metamorphosed limestone; (verb) to pattern like marble. |
| marbly | like marble, marbled > MARBLIER, MARBLIEST. |
| marmarise marmarize | to convert limestone into marble. |
| marmoreal marmorean | of or like marble. Also MARMOREAL. |
| melaphyre | any one of several dark-colored augitic, eruptive rocks allied to BASALT. |
| mesocratic | containing 30-60 per cent of ferromagnesian minerals. |
| migmatite | a type of rock containing igneous and metamorphic elements. |
| minestone | ore, esp. ironstone. |
| monzonite | a PHANERITIC igneous rock that consists of nearly equal percentages of alkali-feldspar and PLAGIOCLASE feldspar and 20-50 percent dark minerals, typically BIOTITE and HORNBLENDE. |
| moonrock | rock brought back from the surface of the moon. |
| mudrock | a PELITE, any rock derived from clay or mud. |
| mudstone | a fine-grained detrital sedimentary rock made up of clay- and silt-sized particles. |
| mugearite | a dark, finely crystalline basic igneous rock, named for Mugeary in Skye. |
| mylonite | a hard, streaky, often granular rock produced by crushing. |
| mylonitic | of or like MYLONITE, a hard, streaky, often granular rock produced by crushing. |
| nappe | a sheet of rock which has moved horizontally over neighbouring strata, as a result of overthrusting or recumbent folding. [Fr. nappe, tablecloth]. |
| norite | a type of rock, a gabbro with rhombic pyroxine. |
| noritic | of or like NORITE, a gabbro with rhombic pyroxine. |
| obsidian | a dark-coloured vitreous lava or volcanic rock. |
| onychite | onyx marble. |
| oolite | a kind of limestone comprising small egg-like grains. |
| oolith | any of the small rounded granules of which OOLITE is composed. |
| oolitic | of or like OOLITE. |
| ophiolite | any of a group of basic and ultrabasic igneous rocks consisting largely of serpentine. |
| ophite | a name given to various green-mottled rocks such as DIABASE and serpentine. |
| ophitic | of or like an OPHITE. |
| pavonazzo | a brightly coloured marble. Pl. PAVONAZZOS. |
| pearlite | ferrite and cementite showing distinct bands. |
| pearlitic | relating to PEARLITE, ferrite and cementite showing distinct bands. |
| pegmatite | a coarsely crystallized rock commonly occurring in igneous intrusions, esp. dykes, and consisting mainly of feldspar and quartz. |
| pelite | any rock derived from clay or mud. |
| pelitic | relating to PELITE, any rock derived from clay or mud. |
| peperino | a volcanic rock, formed by the cementing together of sand, scoria, cinders, etc. |
| petrology | the geological study of rocks. |
| petuntse petuntze | a feldspathic rock used in making Chinese porcelain. [Chinese 'little white brick']. |
| phacoid phacoidal | lens-shaped, lenticular; (of rock) characterized by the presence of lenticular inclusions. |
| phacolith | an intrusive mass of igneous rock situated between strata at the top of an anticline or the bottom of a syncline. |
| phonolite | a compact, feldspathic, igneous rock containing nephelite, hauynite, etc. Thin slabs give a ringing sound when struck. Aka CLINKSTONE. |
| picrite | a dark green igneous rock, consisting largely of chrysolite, with hornblende, augite, biotite, etc. |
| picritic | relating to PICRITE, a dark green igneous rock. |
| pipestone | a kind of clay slate, carved by the Indians into tobacco pipes. |
| pluton | a mass of rock solidified under earth's surface. [Back-formation from German plutonisch]. |
| plutonic | pertaining to or involving the formation of rocks at great depths in the earth's crust. |
| porphyroid | a metamorphic rock having a texture characterized by large crystals set in a finer groundmass. |
| porphyry | a very hard, variegated rock of a purple and white colour, used in sculpture. [Gk. porphyrites, from porphyros, purple]. |
| portland | a kind of cement, having the color of the Portland stone. |
| pozzolan pozzolana puzzolana | volcanic ashes from Pozzuoli, in Italy, used in the manufacture of a kind of mortar which hardens under water. |
| protogine | a kind of granite or gneiss containing a silvery talcose mineral. |
| psammite | a fine-grained rock. |
| psammitic | of or like PSAMMITE, any rock composed of sand-grains. |
| psephite | a rock composed of pebbles, a conglomerate. |
| psephitic | of or relating to pebbles. |
| pumiceous | of or pertaining to pumice; resembling pumice. |
| pumicite | a porous volcanic rock. |
| pumie pumy | pumice. |
| quartzite | a metamorphosed sandstone. |
| quartzose | containing, or resembling, quartz; partaking of the nature or qualities of quartz. |
| ragstone | any of various different kinds of stone of a hard coarse texture, which break up in flat pieces several inches thick. |
| rance | a type of red marble; (verb) to shore up, prop. |
| regolith | a layer of loose rock overlaying solid rock. |
| rhyolite | a highly felsic igneous volcanic rock, typically light in color; the rough volcanic equivalent of granite. |
| rhyolitic | relating to RHYOLITE, a highly felsic igneous volcanic rock. |
| rimrock | an outcrop of resistant rock, esp. one forming a cliff at the edge of a plateau. |
| rockbound | hemmed in by rock, rocky. |
| rockfall | a fall of rock. |
| rockless | being without rocks. |
| rocklike | like a rock. |
| rockwater | water issuing from a rock. |
| roestone | another name for OOLITE, a kind of limestone comprising small egg-like grains. |
| rudaceous | of breccia etc, composed of coarse-grained material. |
| sandstone | a CLASTIC sedimentary rock that is LITHIFIED sand. |
| saprolite | a soft, partially decomposed rock that has remained in its original site. |
| saprolitic | of or like a SAPROLITE. |
| saxonite | an ultrabasic igneous rock consisting of OLIVINE and ENSTATITE. |
| scaglia | a reddish variety of limestone. Pl. SCAGLIAS. |
| schist shist | a type of metamorphic rock consisting of a significant percentage of one or more platy minerals such as one of the micas and/or chlorites. |
| schistose schistous | of or pertaining to schist; having the structure of a schist. |
| schliere | one of a set of streaks of different color or composition in igneous rock. Pl. SCHLIEREN. |
| schlieric | relating to SCHLIEREN. |
| sclate sklate | to slate. |
| scrae | scree, loose rock debris. |
| scree | loose rock debris; a slope at the base of cliff of said debris. |
| shalelike | like SHALE. |
| shaley shaly | of or like shale > SHALIER, SHALIEST. |
| sienite syenite | a coarse-grained igneous rock, allied to granite. |
| sierra | a ridge of mountain and craggy rocks, with a serrated or irregular outline; as, the Sierra Nevada. |
| silicate | any of the compounds regarded as formed from silica and other oxides, which include many rock-forming minerals; (verb) to combine with silica. |
| siliceous silicious | consisting in a noteworthy part of silica, typically quartz. |
| silicify | to convert into or impregnate with silica. |
| siltstone | a rock formed of hardened silt. |
| sklate | see SCLATE. |
| slabstone | flagstone. |
| slate | to roof with slate. |
| slatey slaty | like or containing slate > SLATIER, SLATIEST. |
| slickrock | smooth wind-polished rock. |
| soapstone | a soft soapy rock. |
| spilite | a fine-grained igneous rock of basaltic composition. |
| spilitic | of or like SPILITE, a fine-grained igneous rock of basaltic composition. |
| spilosite | a spotted slate, formed by contact metamorphism. |
| stinkstone swinestone | a kind of LIMESTONE, givign a fetid urinous smell when rubbed. |
| stratal | relating to a STRATUM. |
| stratum | a layer of sedimentary rock. Pl. STRATA or STRATUMS. |
| stylolite | a small columnar rock formation in limestone and other calcareous rocks that is at right angles to the bed, of irregular cross section, with striated sides. |
| swinestone | see STINKSTONE. |
| syenite | see SIENITE. |
| syenitic | of or like SYENITE, a kind of igneous rock. |
| sylvinite | a rock composed of SYLVINE and rock salt. |
| synclinal | of or like a SYNCLINE, a fold of rock layers that is convex downwards. |
| syncline | a fold of rock layers that is convex downwards. Antonym of ANTICLINE. |
| tachylite tachylyte | a vitreous form of basalt. |
| talus | rock detritus or debris at the base of a slope > TALUSES; the ankle bone > TALI. |
| tarras terras trass | an earthy volcanic tuff used as a hydraulic cement. |
| taxite | a kind of volcanic rock. |
| taxitic | relating to TAXITE, a volcanic rock. |
| tectite tektite | a type of small glassy stone, thought to be a product of meteorite impact. |
| tectonic | pertaining to the actual structure of the crust of the earth (or of another planet or a moon), or to general changes affecting it. |
| tektitic | relating to a TEKTITE. |
| tephrite | an igneous rock consisting essentially of plagioclase and either LEUCITE or NEPHELITE, or both. |
| tephritic | of or like TEPHRITE, an igneous rock consisting essentially of plagioclase and either LEUCITE or NEPHELITE, or both. |
| terras | an earthy volcanic tuff used as a hydraulic cement > TERRASES. |
| theralite | a holocrystalline igneous rock composed of PLAGIOCLASE, NEPHELITE and AUGITE. |
| tholeiite | a basaltic rock rich in aluminum. |
| till | glacial drift composed of rock fragments that range from clay to boulder size and randomly arranged without bedding. |
| tillite | indurated TILL, glacial drift composed of rock fragments that range from clay to boulder size and randomly arranged without bedding. |
| tilly | of or like TILL > TILLIER, TILLIEST. |
| tinguaite | a fine-grained igneous rock composed essentially of FELDSPAR, NEPHELINE and AEGIRINE. |
| tonalite | a coarse-grained igneous rock. |
| tonalitic | of or like TONALITE. |
| toph tophe tufa | a rock made of fine volcanic detritus. See also CALCTUFA. |
| torbanite | a shale, almost a coal, once mined for oil at Torbane Hill in Scotland. |
| touchstone | Lydian stone, a highly siliceous (usu black) stone or other stone for testing gold or silver by the colour of the mark each makes on it; (fig.) a criterion, a standard. |
| trachyte | any fine-grained volcanic rock of the alkaline series of intermediate rocks. |
| trachytic | of, pertaining to, or resembling, TRACHYTE, an igneous rock, usually light gray in color and breaking with a rough surface. |
| trap traprock | any fine-grained columnar igneous rock esp. basalt. |
| trappean trappose trappous | of or pertaining to TRAP. |
| trappy | of or pertaining to TRAP, a kind of rock > TRAPPIER, TRAPPIEST. |
| trass | see TARRAS. |
| travertin travertine | a white concretionary form of calcium carbonate, usually hard and semicrystalline, deposited from the water of springs or streams holding lime in solution. |
| tufa | see TOPH. |
| tufaceous | pertaining to TUFA; consisting of, or resembling, tufa. |
| tuff | a general term for all consolidated pyroclastic rock. Not to be confused with TUFA. See also CALCTUFF. |
| variolite | a kind of DIORITE or DIABASE containing imbedded whitish spherules, which give the rock a spotted appearance. |
| veinstone veinstuff | the nonmetalliferous mineral or rock material which accompanies the ores in a vein, as quartz, calcite, barite, fluor spar, etc. |
| ventifact | a stone polished by wind-blown sand. |
| verd | as in verd antique, a dark green mottled impure variety of serpentine. No —S. |
| viridite | an indeterminate green decomposition product in rocks. |
| vug vugg vugh | a small unfilled cavity in a lode or in rock. [Cornish vooga]. |
| vuggy vughy | like a VUG or VUGG, a cavity lined with crystals > VUGGIER, VUGGIEST; VUGHIER, VUGHIEST. |
| wacke | an old name for a decomposed BASALT. |
| whinstone whunstane | a hard and compact rock. |
| xenolith | a rock fragment foreign to the igneous mass in which it occurs. |
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