Sinonimi di Types of rock
andesitea fine-grained tan or grey volcanic rock consisting of plagioclase feldspar, esp andesine, amphibole, and pyroxene anorthositea coarse-grained plutonic igneous rock consisting almost entirely of plagioclase feldspar anthracitea hard jet-black coal that burns slowly with a nonluminous flame giving out intense heat. Fixed carbon content: 86–98 per cent; calorific value: 3.14 × 107–3.63 × 107 J/kg arkosea sandstone consisting of grains of feldspar and quartz cemented by a mixture of quartz and clay minerals basalta fine-grained dark basic igneous rock consisting of plagioclase feldspar, a pyroxene, and olivine: the most common volcanic rock and usually extrusive brecciaa rock consisting of angular fragments embedded in a finer matrix, formed by erosion, impact, volcanic activity, etc chalka soft fine-grained white sedimentary rock consisting of nearly pure calcium carbonate, containing minute fossil fragments of marine organisms, usually without a cementing material cherta microcrystalline form of silica usually occurring as bands or layers of pebbles in sedimentary rock. Formula: SiO2. Varieties include flint, lyddite (Lydian stone) claya very fine-grained material that consists of hydrated aluminium silicate, quartz, and organic fragments and occurs as sedimentary rocks, soils, and other deposits. It becomes plastic when moist but hardens on heating and is used in the manufacture of bricks, cement, ceramics, etc coala combustible compact black or dark-brown carbonaceous rock formed from compaction of layers of partially decomposed vegetation: a fuel and a source of coke, coal gas, and coal tar conglomerateany coarse-grained sedimentary rock consisting of rounded fragments of rock embedded in a finer matrix dioritea dark coarse-grained igneous plutonic rock consisting of plagioclase feldspar and ferromagnesian minerals such as hornblende doleritea dark basic intrusive igneous rock consisting of plagioclase feldspar and a pyroxene, such as augite; often emplaced in dykes dolomitea white mineral often tinted by impurities, found in sedimentary rocks and veins. It is used in the manufacture of cement and as a building stone (marble). Composition: calcium magnesium carbonate. Formula: CaMg(CO3)2. Crystal structure: hexagonal (rhombohedral) dunitean ultrabasic igneous rock consisting mainly of olivine eclogitea rare coarse-grained basic rock consisting principally of garnet and pyroxene. Quartz, feldspar, etc, may also be present. It is thought to originate by metamorphism or igneous crystallization at extremely high pressure felsite or felstoneany fine-grained igneous rock consisting essentially of quartz and feldspar flintan impure opaque microcrystalline greyish-black form of quartz that occurs in chalk. It produces sparks when struck with steel and is used in the manufacture of pottery, flint glass, and road-construction materials. Formula: SiO2 gabbroa dark coarse-grained basic plutonic igneous rock consisting of plagioclase feldspar, pyroxene, and often olivine gneissany coarse-grained metamorphic rock that is banded and foliated: represents the last stage in the metamorphism of rocks before melting granitea light-coloured coarse-grained acid plutonic igneous rock consisting of quartz, feldspars, and such ferromagnesian minerals as biotite or hornblende: widely used for building granodioritea coarse-grained acid igneous rock containing almost twice as much plagioclase as orthoclase: intermediate in composition between granite and diorite gravelan unconsolidated mixture of rock fragments that is coarser than sand greywacke or (U.S.) graywackeany dark sandstone or grit having a matrix of clay minerals gritany coarse sandstone that can be used as a grindstone or millstone hornblenditehornfelsa hard compact fine-grained metamorphic rock formed by the action of heat from a magmatic intrusion on neighbouring sedimentary rocks lamprophyreany of a group of basic igneous rocks consisting of feldspathoids and ferromagnesian minerals, esp biotite: occurring as dykes and minor intrusions lavaany extrusive igneous rock formed by the cooling and solidification of molten lava lignitea brown carbonaceous sedimentary rock with woody texture that consists of accumulated layers of partially decomposed vegetation: used as a fuel. Fixed carbon content: 46–60 per cent; calorific value: 1.28 × 107 to 1.93 × 107 J/kg (5500 to 8300 Btu/lb) limestonea sedimentary rock consisting mainly of calcium carbonate, deposited as the calcareous remains of marine animals or chemically precipitated from the sea: used as a building stone and in the manufacture of cement, lime, etc loessa light-coloured fine-grained accumulation of clay and silt particles that have been deposited by the wind marblea hard crystalline metamorphic rock resulting from the recrystallization of a limestone: takes a high polish and is used for building and sculpture monzonitea coarse-grained plutonic igneous rock consisting of equal amounts of plagioclase and orthoclase feldspar, with ferromagnesian minerals mudstonea dark grey clay rock similar to shale but with the lamination less well developed obsidiana dark volcanic glass formed by very rapid solidification of lava pegmatiteany of a class of exceptionally coarse-grained intrusive igneous rocks consisting chiefly of quartz and feldspar: often occurring as dykes among igneous rocks of finer grain peridotitea dark coarse-grained ultrabasic plutonic igneous rock consisting principally of olivine perknitephyllitea compact lustrous metamorphic rock, rich in mica, derived from a shale or other clay-rich rock pitchstonea dark glassy acid volcanic rock similar in composition to granite, usually intruded as dykes, sills, etc pumicea light porous acid volcanic rock having the composition of rhyolite, used for scouring and, in powdered form, as an abrasive and for polishing pyroxenitea very dark coarse-grained ultrabasic rock consisting entirely of pyroxene minerals quartzitea very hard metamorphic rock consisting of a mosaic of intergrown quartz crystals rhyolitea fine-grained igneous rock consisting of quartz, feldspars, and mica or amphibole. It is the volcanic equivalent of granite sandstoneany of a group of common sedimentary rocks consisting of sand grains consolidated with such materials as quartz, haematite, and clay minerals: used widely in building schistany metamorphic rock that can be split into thin layers because its micaceous minerals have become aligned in thin parallel bands shalea dark fine-grained laminated sedimentary rock formed by compression of successive layers of clay-rich sediment skarnslatea compact fine-grained metamorphic rock formed by the effects of heat and pressure on shale. It can be split into thin layers along natural cleavage planes and is used as a roofing and paving material soapstonesyenitea light-coloured coarse-grained plutonic igneous rock consisting of feldspars with hornblende or biotite trachytea light-coloured fine-grained volcanic rock of rough texture consisting of feldspars with small amounts of pyroxene or amphibole ▷ See rock
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