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Science & Tech > Earth > Rocks

Now updated for CSW19. New words, if any, and new inflections of existing words, are shown in red.

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.
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.
cornbrash a clayey limestone whose presence in the soil affords good growth for cereal crops.
cornstone a silicious limestone favourable for cereal crops.
corsite a variety of DIORITE.
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 graystone a grey volcanic rock.
greywether graywether 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 > HORNFELSES.
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. Plural SCHLIEREN.
schlieren one of a set of streaks of different color or composition in igneous rock. Plural SCHLIERENS.
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.
vugular pertaining to vugs.
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.