| 单词 | igneous rock |
| 例句 | There's that little pause of Canadian restraint, as if to say, "I thought it was obvious," before his devastating, "I'm sorry but of course we were looking for James Monroe/Liechtenstein/igneous rock." Bidding a final, poignant adieu to "Jeopardy!" host Alex Trebek amidst our nation's chaos 2021-01-09T05:00:00Z There’s that little pause of Canadian restraint, as if to say, “I thought it was obvious,” before his devastating, “I’m sorry but of course we were looking for James Monroe/Liechtenstein/igneous rock.” Alex Trebek is asking the right question after his latest cancer setback 2019-10-08T04:00:00Z Inside is yet another ring, dating back at least 2,000 years, made of so-called bluestones — igneous rocks, each weighing between two and four tons, not indigenous to the area. Hiking along Virginia’s Aquia Creek and finding history a stone’s throw from home 2021-04-01T04:00:00Z Some of Rum's igneous rocks have a very similar mineral and chemical content to those found in the Séítah Formation within the Jezero crater on Mars. Nasa collect Rum rocks ahead of Mars space mission 2023-07-28T04:00:00Z Lithium is often found in igneous rocks—magma that crystallized in the crust or lava that cooled on the surface. Major U.S. geological survey aims to uncover minerals critical for batteries and microchips 2023-06-01T04:00:00Z That includes igneous rock to date the crater and sedimentary rock and clays that may contain biosignatures, perhaps even fossilized evidence of microbial life. NASA’s Perseverance Rover May Already Have Evidence of Ancient Martian Life 2023-04-05T04:00:00Z The hillsides consist of a mélange of sheared and metamorphosed sedimentary and igneous rocks, crisscrossed with faults that allow water to seep beneath and destabilize the slopes. In Big Sur, Living With Nature’s Beauty but Trapped by Its Fury 2023-02-04T05:00:00Z As lava cools, it crystallizes into igneous rock, freezing electrons within iron-bearing minerals into patterns that could reveal a magnetic field’s traits, such as its orientation. Mars rover digs up intriguing clues in the hunt for life beyond Earth 2022-11-23T05:00:00Z Heavy REEs—those with high atomic numbers, including dysprosium, yttrium, and terbium—are most commonly extracted from masses of clay formed through eons of weathering of igneous rocks such as granite. It’s electric! Technique could clean up mining of valuable rare earth elements 2022-11-01T04:00:00Z These igneous rocks contain radioactive elements such as uranium. Mars rover nears milestone in ambitious plan to to return first rocks from another planet 2022-09-20T04:00:00Z Collected in September 2021, the rover’s first sample is thought to be igneous rock from an ancient lava flow. NASA’s Perseverance Rover May Already Have Evidence of Ancient Martian Life 2023-04-05T04:00:00Z These are both igneous rock, the term used for any rock that has cooled from a molten state. Astronomy 2016-10-13T00:00:00Z Subduction of oceanic crust at various locations along the west coast and within the accreted terranes prior to their arrival has produced massive volumes of intrusive igneous rocks within the Coast Range. Physical Geology 2015-01-01T00:00:00Z It is this magma that becomes the source for volcanoes and igneous rocks. An Introduction to Geology 2017-01-01T00:00:00Z The granite was formed as intrusive igneous rock approximately 350 million years ago. In Barre, Vt., granite is a way of life — and beyond 2022-06-16T04:00:00Z It spent many of its early months exploring the crater floor — which unexpectedly is made of igneous rocks, a type that forms as molten materials cool. NASA’s Perseverance Rover Begins Key Search for Life on Mars 2022-06-07T04:00:00Z Sedimentary rocks are made of fragments of igneous rock or the shells of living organisms deposited by wind or water and cemented together without melting. Astronomy 2016-10-13T00:00:00Z Intrusive igneous rocks form at depths of several hundreds of metres to several tens of kilometres. Physical Geology 2015-01-01T00:00:00Z This chapter will describe the classification of igneous rocks, the unique processes that form magmas, types of volcanoes and volcanic processes, volcanic hazards, and igneous landforms. An Introduction to Geology 2017-01-01T00:00:00Z But on Mars, many lake-deposited sediments were eroded from igneous rocks and can appear volcanic from space. Mars rover wraps survey of Jezero crater’s surprising volcanic floor 2022-03-09T05:00:00Z That was a scientific jackpot because scientists can date igneous rocks on the basis of the radioactive decay of their chemical elements. NASA’s Perseverance Rover Begins Key Search for Life on Mars 2022-06-07T04:00:00Z Molten rock rises from below to fill the space between the receding plates; this rock is basaltic lava, the kind of igneous rock that forms most of the ocean basins. Astronomy 2016-10-13T00:00:00Z Over time, the igneous rock of the oceanic crust gets covered with layers of sediment, which eventually become sedimentary rock, including limestone, mudstone, chert, and turbidites. Physical Geology 2015-01-01T00:00:00Z These are known as fine-grained extrusive, or volcanic, igneous rocks. An Introduction to Geology 2017-01-01T00:00:00Z Produced volcanically, the igneous rocks on Jezero’s floor contain large olivine crystals that typically form near the bottoms of thick lava lakes and flows. What We Learned from the Perseverance Rover’s First Year on Mars 2022-02-17T05:00:00Z The research involved dunite, a coarse, dense type of igneous rock named after a mountain in New Zealand. Underground carbon-dioxide storage idea is cracked. And that’s actually good. 2022-02-13T05:00:00Z The layers of rock at Salisbury Crags supported his belief that igneous rocks are formed from magma. Calls to allow people to return to Edinburgh's Radical Road 2022-02-01T05:00:00Z Intrusive igneous rock typically crystallizes at depths of hundreds of metres to tens of kilometres below the surface. Physical Geology 2015-01-01T00:00:00Z Figure 4.1: Half Dome, a mass of intrusive igneous rock in Yosemite National Park, now exposed by erosion. An Introduction to Geology 2017-01-01T00:00:00Z Perseverance’s already-collected igneous rock cores can be used to measure the strength of Mars’s ancient magnetic field and to precisely pin ages on the crater’s epochs. What We Learned from the Perseverance Rover’s First Year on Mars 2022-02-17T05:00:00Z Before cooling and forming igneous rocks, molten lava is made of metal and oxygen-containing glasses that are not only tolerant of heat, but also flow when heated. New lava-like coating can stop fires in their tracks 2022-01-06T05:00:00Z "Some of these rocks could have a composition that makes it look igneous, when they could be sedimentary or igneous rocks," Siebach said. Mars' weird geology is making Perseverance's job more complicated 2021-08-26T04:00:00Z To change its position in the rock cycle, intrusive igneous rock has to be uplifted and exposed by the erosion of the overlying rocks. Physical Geology 2015-01-01T00:00:00Z These are known as coarse-grained intrusive, or plutonic, igneous rocks. An Introduction to Geology 2017-01-01T00:00:00Z Percy may be directed back to this spot to try and grab some igneous rocks in the future, Farley says. Crumbly Mars Rock, Not Hardware Flaws, Scuttled Perseverance's First Sample Attempt 2021-08-12T04:00:00Z Zircon, a mineral commonly found in igneous rocks, proves particularly useful. How Do Scientists Determine the Ages of Human Ancestors, Fossilized Dinosaurs and Other Organisms? 2020-08-04T04:00:00Z This land is made of igneous rock fissured with gold. The Fight for the Reindeer 2019-11-18T05:00:00Z Virtually all of the igneous rocks that we see on Earth are derived from magmas that formed from partial melting of existing rock, either in the upper mantle or the crust. Physical Geology 2015-01-01T00:00:00Z This relationship between cooling rates and grain sizes of the solidified minerals in igneous rocks is important for interpreting the rock’s geologic history. An Introduction to Geology 2017-01-01T00:00:00Z It's not terribly surprising to find garnets in igneous rocks. The Astonishing Origin of Garnets in Rhyolite 2019-02-03T05:00:00Z The 300 million-year-old igneous rock on which the Eastern Seaboard is perched does not conduct electricity well. This NASA spacecraft is about to probe one of Earth’s scariest threats — the sun 2018-08-09T04:00:00Z The Spanish noun refers to the hollows in the igneous rock that, after a good rain, transform into watery cradles for tadpoles and fairy shrimp. You’re going where? El Paso, Texas 2018-05-16T04:00:00Z This makes it unique among the minerals that are common in igneous rocks. Physical Geology 2015-01-01T00:00:00Z Cooling history is also related to changes that can occur to the composition of igneous rocks. An Introduction to Geology 2017-01-01T00:00:00Z Sites such as Bear's House — composed of igneous rock, the solid core of what was likely once a volcano — are therefore charged places. What you say can be used in an Edgar Heap of Birds painting: The artist on his way with words 2018-02-14T05:00:00Z Petford, N. Controls on primary porosity and permeability development in igneous rocks. Primordial clays on Mars formed beneath a steam or supercritical atmosphere 2017-12-05T05:00:00Z The answer is a resounding yes when CO2 is injected into the igneous rock basalt, says Matter. Emissions: We have the technology : Nature : Nature Research 2017-10-10T04:00:00Z In most cases, this is sedimentary or igneous rock, but metamorphic rock that reaches the surface and is then reburied can also be considered a parent rock. Physical Geology 2015-01-01T00:00:00Z The slow cooling process allows crystals to grow large, giving the intrusive igneous rock a coarse-grained or phaneritic texture. An Introduction to Geology 2017-01-01T00:00:00Z These are tough igneous rocks of the Cascade mountains. Bad Signs 2017-06-04T04:00:00Z Today, the granular, igneous rock is less popular than engineered stone, commonly referred to as quartz. With countertops, quartz has supplanted granite as the people’s choice 2017-01-19T05:00:00Z “Magnetite is typically something that geologists expect in igneous rocks. To find it in an animal is a bio-chemical anomaly.” Maverick scientist thinks he has discovered a magnetic sixth sense in humans 2016-06-23T04:00:00Z The Bowen reaction series is one of the results of his work, and even a century later, it is an important basis for our understanding of igneous rocks. Physical Geology 2015-01-01T00:00:00Z When lava is extruded onto the surface, or intruded into shallow fissures near the surface and cools, the resulting igneous rock is called extrusive or volcanic. An Introduction to Geology 2017-01-01T00:00:00Z Most of the “meteorwrongs” are actually masses of iron, glassy byproducts from smelting ore called slags, or igneous rocks with small cavities called vesicular rocks. Some Meteorites Are Million-Dollar Finds, Others Are ‘Meteorwrongs’ 2016-04-20T04:00:00Z The stones are volcanic and igneous rocks with precise geological signatures that match the inner horseshoe of smaller rocks at Stonehenge. New Discovery Solves One Mystery of Stonehenge’s Construction 2015-12-07T05:00:00Z Obsidian is an igneous rock that forms when molten material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure. Strange Skills: The Flintknapper 2015-11-07T05:00:00Z The diagram in Figure 3.16 can be used to help classify igneous rocks by their mineral composition. Physical Geology 2015-01-01T00:00:00Z Extrusive igneous rocks have a fine-grained or aphanitic texture, in which the grains are too small to see with the unaided eye. An Introduction to Geology 2017-01-01T00:00:00Z Second, they want igneous rocks, which can be dated on Earth and can help scientists understand the way that Mars formed. Mars scientists tap ancient river deltas and hot springs as promising targets for 2020 rover 2015-08-06T04:00:00Z The palm-like Pandanus candelabrum apparently prefers soil rich in kimberlite — a type of igneous rock that forms in the Earth's crust in huge vertical columns. Rare African plant points the way to diamonds 2015-05-07T04:00:00Z The digital model was a computer simulation of cooling igneous rock. Volcanic Activity, Not Giant Bears, Created Enigmatic Devils Tower 2015-03-10T04:00:00Z It is not uncommon to see an intrusive igneous rock with crystals up to a centimetre long. Physical Geology 2015-01-01T00:00:00Z To avoid these complications, the following figure presents a simplified version of igneous rock nomenclature focusing on the four main groups, which is adequate for an introductory student. An Introduction to Geology 2017-01-01T00:00:00Z We see different igneous rock types, sedimentary rock types... this is a very complex meteorite. Meteorite 'is oldest chunk of Mars' 2013-11-21T02:29:38Z The trouble is that different isotopic tracers yield wildly different dates for the most common variety of Martian meteorites, hunks of igneous rock called shergottites. Solved: The Mystery of the Martian Meteorites 2013-07-26T18:45:00.760Z They are actually the edges of roughly hexagonal columns of igneous rock, similar to other geometric landmarks such as Ireland's Giant's Causeway or Devils Postpile in California. Volcanic Activity, Not Giant Bears, Created Enigmatic Devils Tower 2015-03-10T04:00:00Z These high-temperature feldspars are likely to be found only in volcanic rocks because intrusive igneous rocks cool slowly enough to low temperatures for the feldspars to change into one of the lower-temperature forms. Physical Geology 2015-01-01T00:00:00Z Therefore, most landforms and rock groups that owe their origin to igneous rocks are intrusive bodies. An Introduction to Geology 2017-01-01T00:00:00Z Scientists found the rock lacks magnesium and iron - elements found in igneous rock examined by previous Mars rovers Spirit and Opportunity. NASA's Mars rover finds rock with Earth-like chemistry 2012-10-12T01:31:36Z As I sit on a fragment of igneous rock and look around me, I indeed feel that "the singer is less than his themes." Australian Pictures Drawn with Pen and Pencil 2012-04-02T02:00:28.873Z It is a common constituent of granite and of various igneous rocks. Webster's Unabridged Dictionary 2012-03-24T02:00:23.513Z In classifying intrusive igneous rocks, the first thing to consider is the percentage of ferromagnesian silicates. Physical Geology 2015-01-01T00:00:00Z This explains the wide variety of resulting igneous rocks that are found all over Earth. An Introduction to Geology 2017-01-01T00:00:00Z A variety of pyroxene, usually of a black or dark green color, occurring in igneous rocks, such as basalt; Ð also used instead of the general term pyroxene. Webster's Unabridged Dictionary (2nd 100 Pages) 2012-03-24T02:00:19.387Z From diabases, basalts, andesites and other igneous rocks a third type of hornfels is produced. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 6 "Home, Daniel" to "Hortensius, Quintus" 2012-03-15T02:00:32.250Z A mineral of the feldspar family, commonly occurring in small glassy crystals, also a constituent of some igneous rocks. Webster's Unabridged Dictionary 2012-03-24T02:00:23.513Z The textures of volcanic rocks will be discussed in Chapter 4, so here we’ll only look at the different textures of intrusive igneous rocks. Physical Geology 2015-01-01T00:00:00Z Note that there are exceptions to this generalized layout of volcano types and igneous rock composition. An Introduction to Geology 2017-01-01T00:00:00Z The second most important goal is to find igneous rocks that could be dated by radioisotope analysis to get a better idea of the ages of rocks on Mars. Mars Scientists Propose Landing Sites for Future Rovers 2012-03-01T23:15:03.017Z The original porphyritic, fluidal, vesicular or fragmental structures of the igneous rock are clearly visible in the less advanced stages of hornfelsing, but become less evident as the alteration progresses. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 6 "Home, Daniel" to "Hortensius, Quintus" 2012-03-15T02:00:32.250Z The Flume, on Star Island, is a fine specimen of the intrusion of igneous rock among the harder formation. Nooks and Corners of the New England Coast 2012-02-22T03:00:25.113Z The minerals that make up igneous rocks crystallize at a range of different temperatures. Physical Geology 2015-01-01T00:00:00Z Cross-cutting igneous rocks and sills can be used to bracket the ages of affected, older sedimentary rocks. An Introduction to Geology 2017-01-01T00:00:00Z The igneous rocks of the Vosges, and those of the Alps, Corsica, &c., and the subject of metamorphism occupied his attention. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 10 "David, St" to "Demidov" 2012-02-17T03:00:33.923Z Green and dark-green are the prevalent tints of the hornfelses produced by the alteration of igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 6 "Home, Daniel" to "Hortensius, Quintus" 2012-03-15T02:00:32.250Z The northern coast range is formed by the oldest rocks in the island, consisting chiefly of limestones and marbles with occasional masses of igneous rock. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 8 "Cube" to "Daguerre, Louis" 2012-01-31T03:00:17.257Z The igneous rocks will be described under the various groups of Granitic, Trappean, and Volcanic. Early Days in North Queensland 2012-01-24T03:00:29.987Z This is not to be confused with the igneous texture porphyritic, although the name is derived from the porphyritic texture that is nearly always present in the igneous rocks in a porphyry deposit. An Introduction to Geology 2017-01-01T00:00:00Z All these forms are found in vitreous igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7 "Crocoite" to "Cuba" 2012-01-22T03:00:24.397Z Hornblende, horn′blend, n. a mineral of various colours, found in granite and other igneous rocks that contain quartz. Chambers's Twentieth Century Dictionary (part 2 of 4: E-M) 2012-01-11T03:00:23.770Z The Pliocene is of marine origin, and rests unconformably upon all the older beds, including the Post-oligocene igneous rocks, thus proving that the final folding and the last volcanic outbursts were approximately of Miocene age. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 8 "Cube" to "Daguerre, Louis" 2012-01-31T03:00:17.257Z The structure of igneous rocks, also, is exactly that which would be produced from alluvial deposits subjected during these cyclical movements to the enormous pressure and consequent heating caused by superimposed material. The Energy System of Matter A Deduction from Terrestrial Energy Phenomena 2011-12-21T03:00:36.570Z Note the unweathered igneous rock in the center. An Introduction to Geology 2017-01-01T00:00:00Z They are common constituents of microcrystalline igneous rocks, and often occur as inclusions in larger crystals of other substances. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7 "Crocoite" to "Cuba" 2012-01-22T03:00:24.397Z The other kinds of rocks are known as igneous rocks, which have been melted under the action of heat and become solid on cooling. Cornwall 2011-12-05T03:00:38.530Z Were this the fact, igneous rock should be found about it. The Geography of the Region about Devils Lake and the Dalles of the Wisconsin 2011-11-29T03:00:17.347Z These have very much the same composition as acid igneous rocks such as granite, aplite, hornblende granite, or intermediate rocks such as syenite and quartz diorite. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 2 "Gloss" to "Gordon, Charles George" 2011-10-31T02:00:28.703Z First, the mineral grains containing the isotope formed at the same time as the rock, such as minerals in an igneous rock that crystallized from magma. An Introduction to Geology 2017-01-01T00:00:00Z The formation of these particular sedimentary rocks by weathering of igneous rocks involves only a little carbon dioxide and water. Climatic Changes Their Nature and Causes 2011-10-28T02:00:24.840Z There are as well intrusive veins of igneous rocks. Cornwall 2011-12-05T03:00:38.530Z Clink′stone, a greenish-gray or brownish compact, or very finely crystalline igneous rock, splitting into slabs, which give a metallic clink when struck by a hammer. Chambers's Twentieth Century Dictionary (part 1 of 4: A-D) 2011-10-11T02:01:08.990Z This variety of igneous rock was met with principally at Pemmican Rock, western inlet of Bellot Strait. In the Arctic Seas A Narrative of the Discovery of the Fate of Sir John Franklin and his Companions 2011-10-10T02:00:18.377Z Note the unweathered igneous rock in the center. An Introduction to Geology 2017-01-01T00:00:00Z With the magnetic anomaly data it is possible to distinguish some types of igneous rocks, particularly basalts, against the background of less magnetic material, particularly sediments. Scientist at Work Blog: Scooping Up Arctic Seafloor Data in an Expedition's Homestretch 2011-10-05T17:01:36Z It is composed chiefly of disintegrating quartzite, flanked on the west by igneous rocks. Climbing in The British Isles, Vol. II Wales and Ireland 2011-09-23T02:00:23.653Z Many of the characters of igneous rocks have been reproduced experimentally by fusing together their minerals, or the constituents of their minerals, in the proper proportion. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z It is a gated fortress built of gray igneous rock in northern Sana, in a neighborhood called Hasaba. Magazine Preview: Yemen on the Brink of Hell 2011-07-21T01:01:35Z Phosphorus is an essential element that occurs in the mineral apatite, which is found in trace amounts in common igneous rocks. An Introduction to Geology 2017-01-01T00:00:00Z The geological formation consists largely of primitive or igneous rocks, trappean, basaltic and granite, and the scenery has a peculiarly grand and sombre appearance. Fifty Years In The Northwest With An Introduction And Appendix Containing Reminiscences, Incidents And Notes 2011-06-13T02:00:27.317Z Ultramafics are igneous rocks — formed volcanically — that become capable of carrying electrical current when they are melted back down into magma. Scientists Discover Magma Ocean on Jupiter's Moon Io 2011-06-08T11:20:00Z Massive igneous rocks can be observed to have undergone intense crushing and cleavage, and to have ultimately assumed a crystalline foliated character. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z Ultramafics are igneous rocks — those formed volcanically — which become capable of carrying electrical current when they are melted back down to magma. Scientists discover Magma ocean on Jupiter's moon Io 2011-05-17T09:00:00Z Within the cooling magma, the mineral crystals continue to grow until they solidify into igneous rock. An Introduction to Geology 2017-01-01T00:00:00Z Most of the iron in igneous rocks is contained in mineral, usually silicates, and would be difficult to separate. North America 2011-05-05T02:00:20.027Z Felspar is one of the principal constituents of almost all igneous rocks, such as granite, diorite, and basalt. The New Gresham Encyclopedia Volume 4, Part 3: Estremoz to Felspar 2011-04-14T02:00:59.373Z As the sedimentary rocks have for the most part been laid down under water, and more especially on the sea-floor, they are often spoken of as “aqueous,” in contradistinction to the igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z Diabase, originally an equivalent of diorite; then used for chloritic igneous rocks of the Intermediate series of various grain; and now usually for a type of dolerite in which the felspar is embedded in augite. The New Gresham Encyclopedia Volume 4, Part 1: Deposition to Eberswalde 2011-04-14T02:00:57.977Z They are usually found in igneous rocks, such as granite, rhyolite, and basalt as well as metamorphic rocks and detrital sedimentary rocks. An Introduction to Geology 2017-01-01T00:00:00Z In the case of several of these mines, igneous rock is near at hand, and the ores are believed to owe their concentration largely to the action of heated waters. North America 2011-05-05T02:00:20.027Z Felsite, or Felstone, a hard, compact igneous rock of somewhat flinty appearance, composed usually of quartz and orthoclase felspar intimately mixed, but sometimes of less highly siliceous minerals. The New Gresham Encyclopedia Volume 4, Part 3: Estremoz to Felspar 2011-04-14T02:00:59.373Z Sills, or intrusive sheets, are bed-like masses which have been thrust between the planes of sedimentary or even of igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z Diop�side, a calcium magnesium silicate, of the pyroxene series, occurring in igneous rocks and altered limestones, with a vitreous lustre, and of a pale-green, or a greenish- or yellowish-white colour. The New Gresham Encyclopedia Volume 4, Part 1: Deposition to Eberswalde 2011-04-14T02:00:57.977Z He noticed that in igneous rocks, certain minerals always occur together and these mineral assemblages exclude other minerals. An Introduction to Geology 2017-01-01T00:00:00Z Economic Importance of the Igneous Terranes.—The igneous rocks, as previously noted, are such as have cooled from fusion. North America 2011-05-05T02:00:20.027Z The land is of recent geological formation, the principal ranges being composed of igneous rock, and showing traces of much volcanic disturbance. Encyclopaedia Britannica, 11th Edition, Volume 10, Slice 3 "Fenton, Edward" to "Finistere" 2011-03-14T03:01:00.580Z They present in addition other structures which have been superinduced upon them, and which they share with the unstratified or igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z The zeolites occur very commonly in cavities in igneous rocks, and also in mineral veins. Geology 2011-02-20T03:00:12.660Z Curious as to why, and with the hypothesis in mind that it had to do with the temperature at which the rocks cooled, he set about conducting experiments on igneous rocks in the early 1900s. An Introduction to Geology 2017-01-01T00:00:00Z Under the influence of percolating, heated waters, new minerals are formed in sedimentary or igneous rocks, and rocks once metamorphosed may undergo additional changes. North America 2011-05-05T02:00:20.027Z Tuffs, basalts and other igneous rocks appear also in Montana, Wyoming, California, Oregon, Washington, Idaho, Colorado; also in Central America, the Antillean region and S. America. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 6 "English Language" to "Epsom Salts" 2011-02-19T03:00:59.807Z This substance has been detected in all igneous rocks, especially among the granites, in quantity sufficient, according to the Hon. R.J. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z What is the nature of the jointing in igneous rocks? Geology 2011-02-20T03:00:12.660Z He conducted experiments on igneous rock—grinding combinations of rocks into powder, sealing the powders into metal capsules, heating them to various temperatures, and then cooling them. An Introduction to Geology 2017-01-01T00:00:00Z Although igneous rocks do contain gold, silver, copper, etc., and a large variety of the rarer metals, they are widely disseminated. North America 2011-05-05T02:00:20.027Z Relevant to our study is the apparent continuation of a distinctive belt of igneous rocks — known as rapakivi granites, which are notable for their texture, mineralogy and chemistry — between North America and Antarctica. Scientist at Work: Answering Questions About Antarctica 2011-01-22T16:00:18Z It is among igneous rocks that the progressive stages of metamorphism can be most easily traced. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z What is the nature of the beds of breccia, conglomerate, ash, and tuff, with which contemporaneous igneous rocks are often associated? Geology 2011-02-20T03:00:12.660Z The unmelted country rocks within an igneous rock mass are called xenoliths. An Introduction to Geology 2017-01-01T00:00:00Z Although the igneous rocks sometimes contain valuable ores, they are in many, if not all instances, due to secondary enrichment and are not a result of primary crystallization from fusion. North America 2011-05-05T02:00:20.027Z The contemporaneous igneous rocks include olivine basalts, andesites, trachytes, rhyolites and tuffs, which are pierced by the microgranite of the Black Hill and by several vents filled with agglomerate, as near Swanston. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 10 "Echinoderma" to "Edward" 2011-01-19T03:00:19.027Z There is another type of alteration termed “contact-metamorphism,” which is developed around masses of igneous rock, especially where these have been intruded in large bosses among stratified formations. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z What is the origin of the vesicular structure in igneous rocks? Geology 2011-02-20T03:00:12.660Z Metamorphic processes tend to reset the clocks and smear the igneous rock’s original date. An Introduction to Geology 2017-01-01T00:00:00Z The igneous rocks themselves furnish desirable building stones, such as granite, diorite, porphyry, diabase, etc. North America 2011-05-05T02:00:20.027Z The intrusive igneous rocks forming prominent features in the county are divisible into two main groups, which are separated from each other by a considerable interval of time. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 10 "Echinoderma" to "Edward" 2011-01-19T03:00:19.027Z The textures of igneous rocks likewise comprise a wide series of varieties. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z How may granite be at one and the same time a metamorphic and igneous rock? Geology 2011-02-20T03:00:12.660Z These requirements place some constraints on the kinds of rock suitable for dating, with the igneous rock being the best. An Introduction to Geology 2017-01-01T00:00:00Z The basal portion of the continent, with the exception of certain areas where igneous rocks occur, is formed of metamorphosed terranes. North America 2011-05-05T02:00:20.027Z The deposits at Mount Sirius sit on top of a mesa of Ferrar dolerite igneous rocks, which weather to form curious patterns. Scientist at Work: Rocks, Zircon Zapping and a Big Shrimp 2011-01-07T21:02:35Z Though the igneous rocks occupy extensive areas in some countries, they nevertheless cover a much smaller part of the whole surface of the land than is taken up by the second division or stratified rocks. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z Fragmental Igneous Rocks.—All the igneous rocks briefly described above are more or less distinctly crystalline in texture. Geology 2011-02-20T03:00:12.660Z Metamorphic and igneous rocks here show extremely complex structure, which represents a geologic history told in many chapters. Scientist at Work: Unraveling the History Beneath the Ice 2010-12-28T21:28:12Z The rocks exposed in the mountains are largely of sedimentary origin, but a characteristic feature is the geology, especially to the west, in the presence of extensive volcanic areas and lofty mountains of igneous rocks. North America 2011-05-05T02:00:20.027Z His attention was now largely directed to the study of the artificial production of minerals, to the metamorphism of rocks, and to the genesis of igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 8 "Dubner" to "Dyeing" 2010-12-26T03:00:17.840Z The igneous rocks present a considerable range of composition. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z How do we distinguish the two groups into which igneous rocks are subdivided? Geology 2011-02-20T03:00:12.660Z In volcanic rocks, and in nearly all other kinds of igneous rocks with the exception of granite, biotite occurs to the exclusion of the muscovite. Encyclopaedia Britannica, 11th Edition, Volume 3, Slice 7 "Bible" to "Bisectrix" 2010-12-20T17:12:05.780Z You pass towering, desolate mountains of black and brown igneous rock. Is Yemen the Next Afghanistan? 2010-07-07T00:34:00Z In addition, all the Martian meteorites consist of hard igneous rock; the more fragile sedimentary rock, which is most likely to contain sign of life, falls apart before reaching Earth. NASA team cites new evidence that meteorites from Mars contain ancient fossils 2010-05-04T04:00:00Z They include those masses of mineral matter which, unlike the igneous rocks, can be traced back to a definite origin on the surface of the earth. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z Define what is meant by contemporaneous and subsequent or intrusive igneous rocks. Geology 2011-02-20T03:00:12.660Z The materials yielding these fossils are embedded in a course volcanic agglomerate which gives rise to crags and is pierced by acid and basic igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 6 "Armour Plates" to "Arundel, Earls of" The intrusive igneous rocks belonging to this period are widely distributed and form conspicuous features. Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 5 "Arculf" to "Armour, Philip" In the Mesaba district of Minnesota the Archean consists of a complex of more or less foliated igneous rocks mostly basic in character. Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 4 "Aram, Eugene" to "Arcueil" Batholite, a mass of igneous rock having no visible floor, and presumed to pass down into some region of the earth's crust where molten rocks at one time prevailed over all others. The New Gresham Encyclopedia. Vol. 1 Part 3 Atrebates to Bedlis How does a contemporaneous igneous rock affect the beds upon which it rests? Geology 2011-02-20T03:00:12.660Z It occurs principally in igneous rocks, particularly diorites. The New Gresham Encyclopedia. Vol. 1 Part 2 Amiel to Atrauli Anorthite is an essential constituent of many basic igneous rocks, such as gabbro and basalt, also of some meteoric stones. Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 2 "Anjar" to "Apollo" Lava, which flows hot and fluid, from a volcano, and cooling becomes a sheet of solid rock, is an igneous rock. The Geological Story of the Isle of Wight A third group of breccias is due to movement in a partly consolidated igneous rock, and may be called “fluxion-breccias.” Encyclopaedia Britannica, 11th Edition, Volume 4, Slice 4 "Bradford, William" to "Brequigny, Louis" How are the axes of the prisms in a columnar igneous rock arranged? Geology 2011-02-20T03:00:12.660Z Basalt , a dark brown or black igneous rock. Unexplored! In igneous rocks of all kinds it is invariably present in small amounts as minute acicular crystals, and was one of the first constituents of the rock to crystallize out from the magma. Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 2 "Anjar" to "Apollo" Some igneous rocks solidify under ground under great pressure, and become crystalline rocks such as granite. The Geological Story of the Isle of Wight As now used by road builders, it embraces a large variety of igneous rocks, chiefly those of fine crystalline structure and of dark-blue, gray, and green colors. The Future of Road-making in America A spheroidal structure is occasionally met with amongst some igneous rocks. Geology 2011-02-20T03:00:12.660Z As this igneous rock weathered with time, the rain and the streams washed it into the ocean. Unexplored! Of this range the central feature is the mountain of Kinabalu, which is composed of porphyritic granite and igneous rocks and attains to a height of 13,698 ft. Encyclopaedia Britannica, 11th Edition, Volume 4, Slice 3 "Borgia, Lucrezia" to "Bradford, John" CHARNOCKITE, a series of foliated igneous rocks of wide distribution and great importance in India, Ceylon, Madagascar and Africa. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 8 "Chariot" to "Chatelaine" The igneous rocks are chiefly granite; and granite is formed of orthoclase-feldspar, mica, and quartz. Nature's Miracles, Volume 1 Familiar Talks on Science—World-Building and Life. Earth, Air and Water. Lava, basalt, and obsidian are characteristic types of this group of igneous rocks. Geology 2011-02-20T03:00:12.660Z Near the northern foot of the Caucasus, especially in the neighbourhood of the hot mineral springs of Pyatigorsk, a group of hills of igneous rocks rises above the plain. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 5 "Cat" to "Celt" Granite, porphyry, and other igneous rocks supposed to have consolidated from a melted state at a great depth from the surface. Principles of Geology or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of Geology These are dark slates and thin-bedded grits with enormous masses of interbedded igneous rocks, lavas and ashes, the product of contemporaneous volcanoes. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 3 "Capefigue" to "Carneades" The igneous rocks, then, are the lowest of all; then come the metamorphic rocks; and as before stated, on top of metamorphic rock begins the first evidence of life in its lowest form. Nature's Miracles, Volume 1 Familiar Talks on Science—World-Building and Life. Earth, Air and Water. Some geologists consider it to be invariably an igneous rock; but, as just stated, it sometimes passes into gneiss in such a way as to lead us to infer its metamorphic origin. Geology 2011-02-20T03:00:12.660Z They contain a great variety of sediments and igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 2 "Camorra" to "Cape Colony" A group, whether of alluvial deposits, sedimentary strata, or igneous rocks, referred to a common origin or period. Principles of Geology or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of Geology Throughout, the rocks are crystalline and include gneiss, schist, and marble--the metamorphosed equivalents of a large variety of ancient sedimentary and igneous rocks. Drainage Modifications and Glaciation in the Danbury Region Connecticut State of Connecticut State Geological and Natural History Survey Bulletin No. 30 In Bohemia, North America and Canada igneous rocks have been observed. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 1 "Calhoun" to "Camoens" Granite, however, also occurs as an igneous rock. Geology 2011-02-20T03:00:12.660Z As regards igneous rocks, the Charnwood Forest quarries of Leicestershire, and those of Cornwall, are particularly noted for their granite. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 4 "England" to "English Finance" A simple mineral, generally of a deep red color, crystallized; most commonly met with in mica slate, but also in granite and other igneous rocks. Principles of Geology or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of Geology It is superfluous to cite localities for them as they are among the commonest of igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 6 "Dodwell" to "Drama" In the Ardennes the system is represented by grits and sandstones, shales, slates and quartz schists, and includes also whet slates and some igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 1 "Calhoun" to "Camoens" In the British Islands, and many other non-volcanic regions, we find besides crystalline igneous rocks, abundant traces of loose ejectamenta, which clearly prove the former presence of volcanoes. Geology 2011-02-20T03:00:12.660Z It is also an essential constituent of some pyroxene-granites, diorites and a few other igneous rocks, but the characteristic pyroxene of this class of rocks is augite. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 5 "Dinard" to "Dodsworth" Man observes the annual decomposition of crystalline and igneous rocks, and may sometimes see their conversion into stratified deposits; but he cannot witness the reconversion of the sedimentary into the crystalline by subterranean fire. Principles of Geology or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of Geology Volcanic activity was in abeyance in Europe and in much of Asia, but in America there were many eruptions and intrusions of igneous rock towards the close of the period. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 6 "Coucy-le-Château" to "Crocodile" Mountains of the Secondary Age were often made of Primary sedimentary rocks, or of Primary igneous rocks, so much changed that geologists call them metamorphic rocks. The Boy With the U.S. Miners True igneous rocks occur either in beds or as irregular amorphous masses. Geology 2011-02-20T03:00:12.660Z The color was about right, and he knew datolite was found in igneous rocks of volcanic origin. The Flaming Mountain The inclined strata A are the disturbed formations of the Apennines, into which the ancient igneous rocks a are supposed to have intruded themselves. Principles of Geology or, The Modern Changes of the Earth and its Inhabitants Considered as Illustrative of Geology It is a convenient name for use in the field when doubt occurs as to the real nature of an igneous rock. Volcanoes: Past and Present Even to his relatively untrained eye, this was a place where a volcanic fissure had opened ages ago, allowing igneous rock to thrust sharply upward through the sedimentary layers of the older ground. The Blue Ghost Mystery Occasionally they appear to have been the feeders of the great sheets of igneous rock which here and there occur in their vicinity. Geology 2011-02-20T03:00:12.660Z In the form of isolated grains the mineral is a characteristic constituent of ultrabasic igneous rocks, namely the peridotites and the serpentines which have resulted from their alteration. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 3 "Chitral" to "Cincinnati" Lithologically they are crystalline schists, together with granite, diorite, gabbro and other igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 2 "Chicago, University of" to "Chiton" Great rents had been formed, igneous rocks had boiled up through them; and then in a grand, titanic effort the fire had forced its way up. Silver and Gold A Story of Luck and Love in a Western Mining Camp On the steep slope of igneous rock no grass had managed to get hold, although a few hardy weeds clung to it. The Blue Ghost Mystery The alteration effected by igneous rocks is generally greatest in the case of intrusive masses. Geology 2011-02-20T03:00:12.660Z Many altered igneous rocks owe their green colour to the presence of secondary chlorite. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 3 "Chitral" to "Cincinnati" Through the Mesozoic beds are intruded granitic and other igneous rocks of Tertiary age, and upon the folded Mesozoic foundation rise the volcanic cones of Tertiary and later date. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 2 "Chicago, University of" to "Chiton" It does not occur in distinct crystals with definite outlines, but only as lamellar masses in deep-seated igneous rocks, principally gabbro, of which it is an essential constituent. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 3 "Destructors" to "Diameter" In all the wide bowl of the great crater top was nothing but dead ashes of fires gone long centuries before, coarse, igneous rock—nothing to set the little nerves of one's spine to tingling. Two Thousand Miles Below Chemical changes also take place in the case of many igneous rocks, the result being that a weathered 'crust' forms wherever such rocks are exposed to the action of the atmosphere. Geology 2011-02-20T03:00:12.660Z When the exposed land consists of several unlike kinds of sedimentary strata, or igneous rocks, or both, denudation produces changes proportionably more heterogeneous. Essays: Scientific, Political, & Speculative, Vol. I Several pieces of shale lay exposed under a fold of igneous rock. The Long Voyage Contemporaneous igneous rocks are generally absent in the American Devonian, but in Nova Scotia and New Brunswick there appear to be some. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 3 "Destructors" to "Diameter" He had descended a thousand feet, he was estimating, when the black igneous rocks blazed blindingly with a reflected light like that of a thousand suns. The Finding of Haldgren These form the Fragmental group of igneous rocks. Geology 2011-02-20T03:00:12.660Z Again, it is fast becoming an acknowledged truth that igneous rock, of whatever kind, is the product of sedimentary strata which have been completely melted. Essays: Scientific, Political, & Speculative, Vol. I Some igneous rocks, especially lavas, are glassy; others are so fine grained that the crystals cannot be seen. Boy Scouts Handbook The First Edition, 1911 It was surrounded by huge blocks of orange rock, the igneous rock which is the outstanding feature of the Martian desert landscape. The Martian Cabal The harder limestones, some sandstones, pebbles from many of the gravel deposits and practically all of the igneous rocks make satisfactory aggregates for the concrete road. American Rural Highways But, for sake of clearness, we have reserved special account of the structure and mode of occurrence of metamorphic and igneous rocks to this place. Geology 2011-02-20T03:00:12.660Z A hard skeleton of igneous rock, with clayey soil for flesh, riven and seamed and pitted, crumbling and dusty in the sun, ever disintegrating with wind and water and frost. Rimrock Trail The name is applied in America to a round piece of basic igneous rock. Austral English A dictionary of Australasian words, phrases and usages with those aboriginal-Australian and Maori words which have become incorporated in the language, and the commoner scientific words that have had their origin in Australasia The weathering of sedimentary rocks proceeds along lines already indicated for the igneous rocks. The Economic Aspect of Geology Many granitic and volcanic landscapes are variegated in places by accidental beds of sedimentary rock; and conversely occasional sedimentary landscapes are set off by intrusions of igneous rocks. The Book of the National Parks When the igneous rock itself is examined, its upper portions are often observed to be scoriaceous or cinder-like, and the under portions likewise frequently exhibit a similar appearance. Geology 2011-02-20T03:00:12.660Z Crystals are found as a rarity in the amygdaloidal cavities of igneous rocks. Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 3 "Banks" to "Bassoon" In ten years he is proved utterly wrong by that microscopist who has detected animal remains in an igneous rock. The Voyage Alone in the Yawl "Rob Roy" The magnetite crystals of these deposits interpenetrate with the other constituents of an igneous rock, commonly of a gabbro type, and the deposits themselves are essentially igneous rocks. The Economic Aspect of Geology The principal one of many igneous rocks, it is liquefied under intense heat and afterward cooled under pressure. The Book of the National Parks Not unfrequently, however, an igneous rock will preserve the same texture throughout. Geology 2011-02-20T03:00:12.660Z In current usage the term includes a large variety of types of igneous rock belonging to the basic subdivision, dark in colour weathering to brown, and comparatively rich in magnesia and iron. Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 3 "Banks" to "Bassoon" Basalt is an igneous rock composed largely of augite and felspar, which are silicate crystals of calcium, potassium, alumina, etc., of which the Moonstone is a variety. Second Sight A study of Natural and Induced Clairvoyance We can only speculate as to causes of the occurrence of valuable minerals in certain igneous rocks and not in others. The Economic Aspect of Geology There are no proofs that the igneous rocks were produced more abundantly at remote periods. The World's Greatest Books — Volume 15 — Science It will be noticed that the contemporaneous igneous rocks form a series of escarpments rising one above the other. Geology 2011-02-20T03:00:12.660Z Then volcanoes burst forth; the igneous rocks sent up mountains of liquid flame, and the paste of the streaming porphyry and basalt began to congeal. Bouvard and Pécuchet A Tragi-comic Novel of Bourgeois Life Captain DeCastros had withdrawn to a level outcropping of igneous rock and sat staring at the nothing where the greenish-black sky met the pale gray horizon. The Marooner Mineral products formed by weathering from common igneous rocks include soils, clay, bauxite, and certain iron, chromite, and nickel ores. The Economic Aspect of Geology However that may be, metals were brought up with the igneous rocks, and one of these metals is copper. Diggers in the Earth Contemporaneous igneous rocks are frequently associated with more or less regular beds of breccia, conglomerate, ash, tuff, &c. Geology 2011-02-20T03:00:12.660Z Many caves pierce the igneous rock of the Hawaiian group, some with entrances below the ocean level, and discovered only by accident. Myths & Legends of our New Possessions & Protectorate It is, in fact, a true igneous rock. Chambers's Edinburgh Journal, No. 458 Volume 18, New Series, October 9, 1852 The deposition of ores of igneous source in the country rock into which the igneous rocks are intruded is a phase of contact metamorphism. The Economic Aspect of Geology When the igneous rocks were thrown up to the surface of the earth, they brought various metals with them. Diggers in the Earth The strata are bent down towards the central plug of igneous rock, and are generally more or less altered at the line of junction. Geology 2011-02-20T03:00:12.660Z The volcanic fires have been more active there; and though that may have been thousands of years ago, the igneous rocks in many places look as if freshly upheaved. The Scalp Hunters The principal discharge is from an orifice thirty feet broad, opening beneath a ledge of igneous rocks, nearly on a level with the bottom of the ravine. The Continental Monthly, Vol. 6, No 3, September 1864 Devoted To Literature And National Policy The great deposits of Rio Tinto, Spain, which produce about half of the world's pyrite, were formed by replacement of slates by heated solutions from nearby igneous rocks. The Economic Aspect of Geology "This stone was a brown, igneous rock, its longest axis about eight feet, and on the eastern face, which had an angle of about forty-five degrees, was the deep-cut inscription." The Book of the Damned Limestones weather much more rapidly than clay-rocks; and augitic igneous rocks, as a rule, disintegrate more readily than the more highly silicated species. Geology 2011-02-20T03:00:12.660Z The Malutis consist of beds of sandstone and shale, overlaid by an outflow of igneous rock from two to five thousand feet thick. Impressions of South Africa It is to the metamorphic formation that the abundance of mineral ores is due, and the igneous rocks which have given rise thereto—the granites, basalts, diorites, porphyries, and others. Mexico Its Ancient and Modern Civilisation, History, Political Conditions, Topography, Natural Resources, Industries and General Development Granite and basalt as technically defined are very common igneous rocks,—so common that the names are sometimes used to classify igneous rocks in general into two great groups, the granitic and the basaltic. The Economic Aspect of Geology Near the base of the volcanic series intrusive igneous rocks of Carboniferous age appear in the form of sills and bosses, as, for instance, the oval mass of olivine-basalt on Suidhe Hill. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 4 "Bulgaria" to "Calgary" What is the general structure of a contemporaneous igneous rock? Geology 2011-02-20T03:00:12.660Z The summit of Machacha is composed of a dark igneous rock, apparently a sort of amygdaloidal trap, with white and greenish calcareous crystals scattered through it. Impressions of South Africa His observations on the igneous rocks of south Tirol compared with those of Christiania afford much information on the relations of the granitic and basic rocks. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" It has been estimated that about 65 per cent of the igneous rocks are of the granitic group and 35 per cent of the basaltic group. The Economic Aspect of Geology It is a common product of alteration in igneous rocks, and frequently occurs as well-developed crystals in association with zeolites lining the amygdaloidal cavities of basaltic and other rocks. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 4 "Bulgaria" to "Calgary" What is the general texture of a contemporaneous igneous rock? Geology 2011-02-20T03:00:12.660Z Thousands of miles of the earth's surface must once have presented the lurid glow of a vast furnace full of igneous rocks. Fables of Infidelity and Facts of Faith Being an Examination of the Evidences of Infidelity The crystals are found attached to the walls of cavities in decomposed igneous rocks and crystalline schists; it is also found as minute isolated crystals in many sedimentary rocks. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3 "Brescia" to "Bulgaria" As a whole, the mineral products formed directly in igneous rocks constitute a much less important class than mineral products formed in other ways, as described below. The Economic Aspect of Geology Like labradorite and anorthite, it is a common constituent of basic igneous rocks, such as gabbro and basalt. Encyclopaedia Britannica, 11th Edition, Volume 4, Part 4 "Bulgaria" to "Calgary" What relation do they occasionally bear to sheets of igneous rock? Geology 2011-02-20T03:00:12.660Z Shouldn't have known where to look for you either, after this storm among the aqueous or the igneous rocks. Melbourne House The Catoctin Belt itself may be described as a broad area of igneous rocks bordered by two lines of Lower Cambrian sandstones and slates. History and Comprehensive Description of Loudoun County, Virginia The same weathering processes described above for igneous rocks cause considerable changes of economic significance in deposits formed as igneous after-effects. The Economic Aspect of Geology Mica schist crowned some of the heights on the watershed, then gneiss, and now, as we descend further, we have igneous rocks of more recent eruption, porphyry and gneiss, with hornblende. The Last Journals of David Livingstone, in Central Africa, from 1865 to His Death, Volume I (of 2), 1866-1868 What is a neck of intrusive igneous rock, and how have the strata surrounding it been affected? Geology 2011-02-20T03:00:12.660Z Haloes are not found in the younger igneous rocks. The Birth-Time of the World and Other Scientific Essays Over the surface of the igneous rocks are scattered occasional outliers of the Lower Cambrian slate; but far the greater part of the surface of the belt is covered by the igneous rocks. History and Comprehensive Description of Loudoun County, Virginia They are not themselves igneous rocks and they do not constitute pegmatites, but they often grade into pegmatites and belong to the same general stage in the sequence of events. The Economic Aspect of Geology As at Chilolé hill, we have igneous rocks, apparently trap, capped with masses of beautiful white dolomite. The Last Journals of David Livingstone, in Central Africa, from 1865 to His Death, Volume I (of 2), 1866-1868 Mention some of the contrasts between intrusive and contemporaneous igneous rocks. Geology 2011-02-20T03:00:12.660Z Keeping the figures to round numbers we find that this amount of sodium involves the denudation of about 80 x 1016 tonnes of average igneous rock to 53 x 1016 tonnes of average sediment. The Birth-Time of the World and Other Scientific Essays The igneous rocks have also been much folded and crumpled, but on account of their lack of distinctive beds the details of folds can not well be traced among them. History and Comprehensive Description of Loudoun County, Virginia The ores of this class are clearly deposited from vagrant solutions which wander through openings of all kinds in the igneous rock and outward into the adjacent country rocks. The Economic Aspect of Geology Reverse a portion, and give an igneous rock. St. Nicholas, Vol. 5, No. 5, March, 1878 But both contortion and faulting may be due, on a small scale, to local causes, such as the intrusion of igneous rocks, the consolidation of strata, the falling in of old water-courses, &c. Geology 2011-02-20T03:00:12.660Z The viscous movements of siliceous materials, and the out-pouring of igneous rocks which often attend mountain elevation, would find an explanation in such temperatures. The Birth-Time of the World and Other Scientific Essays The metamorphism of the igneous rocks is regional in nature and has the same increase from west to east as the sediments. History and Comprehensive Description of Loudoun County, Virginia Evidence is accumulating in many mining districts that ore deposits of these igneous associations were deposited with a rough zonal arrangement about the igneous rock. The Economic Aspect of Geology The thickness of the entire series varies from 4000 to as much as 12,000 feet, according as it contains more or less of interstratified igneous rocks. The Ancient Life History of the Earth A Comprehensive Outline of the Principles and Leading Facts of Palæontological Science Subdivisions.—In their chemical and mineralogical composition, igneous rocks offer great variety; but they all agree in having felspar for their base. Geology 2011-02-20T03:00:12.660Z In the derivation of the sediments from the igneous rocks there is a loss by solution of about 33 per cent; _i.e._ The Birth-Time of the World and Other Scientific Essays It was the wonderful passage driven through the first area of igneous rocks before we reached the quarry country of the Tiniti. The Certainty of a Future Life in Mars As the igneous rocks are so much more abundant than the sedimentary rocks, the percentage of feldspars in the earth approaches the former rather than the latter figure. The Economic Aspect of Geology This rapid marks the place where the granite, or igneous rock, intrudes, rising at a sharp angle, sloping upward down the stream, reaching the height of 1300 feet about one mile below. Through the Grand Canyon from Wyoming to Mexico There has been much difference of opinion as to the origin of granite—some holding it to be an igneous rock, others maintaining its metamorphic origin. Geology 2011-02-20T03:00:12.660Z This, however, in no way relieves us of the necessity of tracing to the ocean the substances dissolved from the igneous rocks. The Birth-Time of the World and Other Scientific Essays Shouldn't have known where to look for you either, after this storm—among the aqueous or the igneous rocks. Melbourne House, Volume 1 The production of soil from sedimentary rocks involves the same processes as alter igneous rocks; but, starting from rocks of different composition, the result is of course different in some respects. The Economic Aspect of Geology The Wrekin is composed of igneous rocks, and is one of the most remarkable examples of eruptive trap in England. What to See in England A Guide to Places of Historic Interest, Natural Beauty or Literary Association Occasionally we meet with igneous rocks which are more or less vesicular and amygdaloidal throughout their entire mass. Geology 2011-02-20T03:00:12.660Z For this purpose we first compare the average chemical composition of the sedimentary and the igneous rocks. The Birth-Time of the World and Other Scientific Essays They are composed of a kind of igneous rock not found anywhere near Wiltshire. Wanderings in Wessex An Exploration of the Southern Realm from Itchen to Otter The Corocoro copper deposits of Bolivia occur in beds of sandstone with no igneous rocks in the vicinity. The Economic Aspect of Geology Strong arguments against the theory that the leaching of superficial igneous rocks has supplied the materials filling mineral veins, are furnished by the facts observed in the districts where igneous rocks are most prevalent, viz.: Scientific American Supplement, No. 446, July 19, 1884 Where the igneous rocks prevail, the coast is finely indented; where the sandstones abound, it is gently curved. The Atlantic Monthly, Volume 07, No. 40, February, 1861 The rock in general, more especially the primary igneous rock, is not stable in presence of the atmosphere and of water. The Birth-Time of the World and Other Scientific Essays Upon the shore he found an out-cropping of brittle, igneous rock. Beasts of Tarzan Seldom do the ores extend more than 1,000 feet away from the igneous rock. The Economic Aspect of Geology The same may be said of the Pancake Range and other mountain chains of igneous rock in Nevada, while the adjacent ranges composed of sedimentary rocks are rich in ore deposits of various kinds. Scientific American Supplement, No. 446, July 19, 1884 With regard to the older igneous rocks, the enormous amount they have suffered from denudation is a prominent feature. The Project Gutenberg Encyclopedia Volume 1 of 28 We see, then, that the 27 x 1016 tonnes of substances leached from the parent igneous rocks have had a threefold destination. The Birth-Time of the World and Other Scientific Essays Cribbens hunted for "contacts," closely examining country rocks and out-crops, continually on the lookout for spots where sedimentary and igneous rock came together. McTeague The view has also been advanced that the ores originated in the limestone before the advent of the igneous rocks. The Economic Aspect of Geology But we have conclusive evidence that the gold was there in Archæan times, while the igneous rocks are all of modern, probably of Tertiary, date. Scientific American Supplement, No. 446, July 19, 1884 The rock has probably been derived by dynamic metamorphism, from a coarse igneous rock like a gabbro. The Long Labrador Trail There, doubtless, in some profound chasm in the igneous rocks, was the dwelling so vainly sought for until now. The Mysterious Island It is very high, and is composed principally of igneous rock, with a little ironstone, much the same as the ranges down the country. Explorations in Australia The Journals of John McDouall Stuart A platinum arsenide, called sperrylite, is sometimes found associated with sulphide minerals in basic igneous rocks. The Economic Aspect of Geology The arguments against the theory that mineral veins have been produced by the leaching of superficial igneous rocks are in part the same as those already cited against the general theory of lateral secretion. Scientific American Supplement, No. 446, July 19, 1884 The rock has been derived by dynamic metamorphism from a basic igneous rock. The Long Labrador Trail The highest mountain is Kinabalu, in the north, about 4,500 metres above the sea and composed of "porphyritic granite and igneous rocks." Through Central Borneo; an Account of Two Years' Travel in the Land of Head-Hunters Between the Years 1913 and 1917 Four miles from the creek it is rough and stony, composed of igneous rock, with scrub, mulga, and plenty of grass quite to the top. Explorations in Australia The Journals of John McDouall Stuart Pumice is solidified rock froth formed by escape of gases from molten igneous rocks at the surface. The Economic Aspect of Geology Their gaseous foundation there would be as firm as igneous rock here. Ancient and Modern Physics It is an isolated, extinct volcano surrounded by igneous rocks, lavas, andesites, and basalts. Inca Land Explorations in the Highlands of Peru The beacons were found to be part of a horizontal, stratified series of sandstones underlying the igneous rock. The Home of the Blizzard Being the Story of the Australasian Antarctic Expedition, 1911-1914 The remainder of the well passes through igneous rock. The Earth as Modified by Human Action From the beginning of history the principal source of rubies has been upper Burma, where the stones are found in limestone or marble near the contact with igneous rocks, associated with high-temperature minerals. The Economic Aspect of Geology Up-shootings of igneous rock through fractures in water formations were common; but here was the first instance where water-formed rock had been so projected. Sketches New and Old, Part 3. The igneous rock sits squarely upon the level sandstone, like a row of upright books standing upon a shelf. Time and Change The "erratics" comprised a great variety of metamorphic and igneous rocks, and, on a more limited scale, sedimentary types. The Home of the Blizzard Being the Story of the Australasian Antarctic Expedition, 1911-1914 Man observes the annual decomposition of crystalline and igneous rocks, and may sometimes see their conversion into stratified deposits; but he cannot witness the reconversion of the sedimentary into the crystalline by subterranean heat. The Harvard Classics Volume 38 Scientific Papers (Physiology, Medicine, Surgery, Geology) In igneous rock the ore-bearing solutions may have altered the wall rock to a dense mixture of quartz, sericite, and chlorite. The Economic Aspect of Geology The whole country I had travelled over, is composed of sandstone, with probably occasional outbreaks of igneous rocks, as indicated by the rich black soil. Journal of an Overland Expedition in Australia : from Moreton Bay to Port Essington, a distance of upwards of 3000 miles, during the years 1844-1845 They are for the most part composed of primary igneous rocks, amongst which there is a general distribution of iron, and perhaps of other metals. Expedition into Central Australia This familiar rock may be studied as an example of the second great group of rocks,—the unstratified, or igneous rocks. The Elements of Geology But the geological structure of the Pentland Hills, near Edinburgh, shows that igneous rocks were there formed during the newer part of the Devonian or "Old Red" period. The Student's Elements of Geology Certain minerals, such as magnetite, ilmenite, spinel, corundum, etc., are often found as primary segregations within the mass of igneous rock. The Economic Aspect of Geology The creek here consists of a close chain of fine rocky water-holes; the rock is principally clay, resembling very much a decomposed igneous rock, but full of nodules and veins of iron-stone. Journal of an Overland Expedition in Australia : from Moreton Bay to Port Essington, a distance of upwards of 3000 miles, during the years 1844-1845 This tract seemed crushed under a rain of enormous ejected rocks of trap, basalt, granite, and all kinds of igneous rocks. A Journey to the Interior of the Earth A theory held by many refers the ultimate source of the iron to the igneous rocks of the Archean. The Elements of Geology This is also another form of igneous rock, admitting of every variety of composition. The Student's Elements of Geology Furthermore, the quartz gangue near the igneous rock is likely to contain minerals characteristic of hot solutions, while farther away such minerals as dolomite and calcite appear in the gangue, suggestive of cooler conditions. The Economic Aspect of Geology The sand in the bed of the river contains very minute particles of igneous rock. Journal of an Overland Expedition in Australia : from Moreton Bay to Port Essington, a distance of upwards of 3000 miles, during the years 1844-1845 This water filled the fissures caused either by the cooling of the earth's crust, or formed by sudden upheavals of the igneous rocks. Getting Gold: a practical treatise for prospectors, miners and students Such intrusions are accompanied —whether as cause or as effect is still hardly known—by deformations, and their masses of igneous rock are thus found as the core of many great mountain ranges. The Elements of Geology The igneous rocks of the Westerwald, and of the mountains called the Siebengebirge, consist partly of basaltic and partly of trachytic lavas, the latter being in general the more ancient of the two. The Student's Elements of Geology The accessible deposits of the deep zone are associated with plutonic igneous rocks which have been deeply eroded, and not with surface lavas. The Economic Aspect of Geology This was the first igneous rock of more recent date, that we had met with since leaving Separation Creek, and the upper Lynd. Journal of an Overland Expedition in Australia : from Moreton Bay to Port Essington, a distance of upwards of 3000 miles, during the years 1844-1845 At the end of the Eocene a great upheaval occurred; there were foldings and crumplings, igneous rock was thrust into the distorted mass, and the islands were considerably elevated above the sea. The Bontoc Igorot Masses of igneous rock cannot be intruded within the crust without an accompanying deformation on a scale corresponding to the bulk of the intruded mass. The Elements of Geology Of these igneous rocks I shall treat more particularly in the sequel. The Student's Elements of Geology They may be intruded by igneous rocks, causing considerable chemical, mineralogical, and structural changes. The Economic Aspect of Geology Although surrounded on all sides by islands of volcanic origin, Borneo differs from them in presenting but small traces of volcanic activity, and in consisting of ancient masses of igneous rock and of sedimentary strata. The Pagan Tribes of Borneo Quartz and other igneous rocks were also scattered about, lying like superficial accumulations in the dips at the foot of the hills, and red sandstone conglomerates clearly indicated the presence of iron. The Discovery of the Source of the Nile The strata deposited at various times about their flanks have been infolded by later crumplings with the original mountain mass, and have been repeatedly crushed, inverted, faulted, intruded with igneous rocks, and denuded. The Elements of Geology Their weapons and tools were polished stone; their hammers and hatchets and adzes, their lance heads and their arrow tips, were of the hardest igneous rock—chipped and ground with patient labour. Short History of Wales It is estimated that the feldspars make up 50 per cent of all the igneous rocks and 16 per cent of the sedimentary rocks. The Economic Aspect of Geology Ancient igneous rocks such as granite lie intricately mingled with old and highly metamorphosed sediments. The Red Man's Continent: a chronicle of aboriginal America Concretions in aqueous and igneous rocks compared. -in tuff. -of obsidian. Volcanic Islands Where the highlands are of igneous rock, such as granite, and mechanical disintegration is going on more rapidly than chemical decay, these conditions are recorded in the nature of the deposits laid offshore. The Elements of Geology In no other part of Timor do there appear to be any recent igneous rocks, so that it can hardly be classed as a volcanic island. The Malay Archipelago, the land of the orang-utan and the bird of paradise; a narrative of travel, with studies of man and nature — Volume 1 The weathering of a highly acid igneous rock with much quartz produces a residual soil with much quartz. The Economic Aspect of Geology The highest rock seen is a fine sandstone of closer grain than that at Tette, and quite metamorphosed where it comes into contact with the igneous rocks below it. A Popular Account of Dr. Livingstone's Expedition to the Zambesi and its tributaries And of the Discovery of Lakes Shirwa and Nyassa, 1858-1864 Since the specimens have become dry, it is rather more easy to distinguish the decomposed igneous rocks from the sedimentary tuffs. Volcanic Islands They are considered by perhaps the majority of the geologists who have studied them most carefully to be igneous rocks intruded in a molten state among the sedimentary rocks involved with them. The Elements of Geology He therefore introduces a cooling of one small underground injection, and then the pumping in of other lava, or porphyry, or granite, into the previously consolidated and first-formed mass of igneous rock. Darwin and Modern Science Shales may weather into products more nearly like those of the weathering of igneous rocks. The Economic Aspect of Geology Below Sinamané’s the banks are often worn down fifty feet, and composed of shingle and gravel of igneous rocks, sometimes set in a ferruginous matrix. A Popular Account of Dr. Livingstone's Expedition to the Zambesi and its tributaries And of the Discovery of Lakes Shirwa and Nyassa, 1858-1864 They have a composition roughly similar to the associated igneous rock, but usually a different proportion of minerals. The Economic Aspect of Geology In the igneous rocks copper, next to iron, is the most common of all the useful metals, and it was especially abundant in the Keweenawan lavas. The Elements of Geology Aplites are fine-grained acid igneous rocks of somewhat the same composition as the pegmatites and often show the same general relations to ores. The Economic Aspect of Geology Only this combination of the three sediments will yield an average composition comparable with that of the parent igneous rocks. The Economic Aspect of Geology Heat and gases may be added beneath the surface by contact with or contributions from cooling igneous rocks. The Economic Aspect of Geology Granites and other coarse-grained igneous rocks do not cement well and are not resistant to abrasion. The Economic Aspect of Geology It is the outcropping edge of a sheet of ancient igneous rock, which rests on stratified sandstones and is overlain by strata of the same series. The Elements of Geology They occur in limestones and shales and are not associated with igneous rocks. The Economic Aspect of Geology Sedimentary rocks are formed from the breaking down of igneous rocks, and the origin of rocks therefore starts with the formation of igneous rocks. The Economic Aspect of Geology Chromite is a common minor constituent of basic igneous rocks of the peridotite and pyroxenite type. The Economic Aspect of Geology It is formed under a variety of conditions, but is always ascribed to solutions coming from nearby igneous rocks. The Economic Aspect of Geology This name is generally applied to huge irregular masses of coarsely crystalline igneous rock lying in the midst of other formations. The Elements of Geology The materials of the ore minerals are believed to have been derived from the igneous rocks and to have been deposited by hot solutions. The Economic Aspect of Geology Some of the igneous rocks are themselves "mineral" products, as for instance building stones and road materials. The Economic Aspect of Geology The original home of platinum is in basic igneous rocks, such as peridotites, pyroxenites, and dunites, where it has been found in small, scattered crystals intergrown with olivine, pyroxene, and chromite. The Economic Aspect of Geology In the vicinity of the most important mines no igneous rocks have been observed, and the origin of the ores has not been worked out. The Economic Aspect of Geology These vast bodies of igneous rock, which may reach hundreds of miles in diameter, differ little from bosses except in their immense bulk. The Elements of Geology About five per cent of the world's production of iron ore is from bodies of magnetite formed in association with igneous rocks. The Economic Aspect of Geology Certain special varieties of igneous rocks, known as pegmatites, carry coarsely crystallized mica and feldspar of commercial value, as well as a considerable variety of precious gems and other commercial minerals. The Economic Aspect of Geology The copper was probably deposited by hot solutions related to the igneous rocks, either issuing from the magmas or deriving heat and dissolved material from them. The Economic Aspect of Geology The ultimate source of salt deposits is the sodium and chlorine of igneous rocks. The Economic Aspect of Geology Sheets of igneous rocks are sometimes found interleaved with sedimentary strata, especially in regions where the rocks have been deformed and have suffered from volcanic action. The Elements of Geology No igneous rocks are known in the vicinity. The Economic Aspect of Geology A special phase of consolidation and cementation is produced near intrusive igneous rocks through the action of the heat and pressure and the expelled substances of the igneous rock. The Economic Aspect of Geology The weathering of a basic igneous rock, as in Cuba, may produce important residual iron ore deposits, which are also used as soils. The Economic Aspect of Geology Their principal occurrence is in distinct fissure veins in igneous rocks, with more or less replacement of the wall rock. The Economic Aspect of Geology We infer that the igneous rock when in a molten state was forced between the strata, much as a card may be pushed between the leaves of a closed book. The Elements of Geology Mercury deposits are in general related to igneous rocks, and have associations which indicate a particular type of igneous activity. The Economic Aspect of Geology In other words, anamorphism tends toward the reproduction of igneous rocks, though it seldom fully accomplishes this result. The Economic Aspect of Geology Magnetites containing titanium, which prevents their use at the present time, are known in many parts of the world as segregations in basic igneous rocks. The Economic Aspect of Geology Iron ores due to weathering of igneous rocks. The Economic Aspect of Geology The nucleus of igneous rock is four miles in diameter and more than a mile in depth. The Elements of Geology These minerals are formed mainly under high temperatures, either during the original solidification of igneous rocks, or as constituents of the pegmatites which follow the crystallization of the main igneous masses. The Economic Aspect of Geology For instance, an igneous rock may become a schist without going through the intermediate stage of sedimentation. The Economic Aspect of Geology Titaniferous magnetites, formed in many basic igneous rocks by the segregation of certain iron-bearing materials into irregular masses, contain large quantities of ilmenite which are not commercially available under present metallurgical processes. The Economic Aspect of Geology They are in fairly close proximity to igneous rocks, and magnesia-bearing solutions issuing from these rocks are believed to have dissolved out the calcium carbonate of the dolomite and replaced it with magnesium carbonate. The Economic Aspect of Geology In these changes heated waters and vapors from the masses of igneous rocks undoubtedly play a very important part. The Elements of Geology The original rock was a highly magnesian igneous rock of the peridotite type, which is very unstable under weathering conditions, and rapidly alters to serpentine. The Economic Aspect of Geology More sediments are formed than are changed to schists and gneisses, and more schists and gneisses are formed than are changed back to igneous rocks. The Economic Aspect of Geology A second group of copper ores in igneous rocks is made up of deposits in distinct fissure veins and as replacements along such veins. The Economic Aspect of Geology This primary ore, or protore, was clearly formed after the solidification of the igneous rocks, though soon after, by solutions from igneous sources which followed fractured and shattered zones. The Economic Aspect of Geology The most thoroughly metamorphosed rocks may sometimes be traced out into unaltered sedimentary or igneous rocks, or among them may be found patches of little change where their history maybe read. The Elements of Geology When the associated gangue and country rock are less soluble than the copper—as is common with quartz and igneous rocks—the oxide zone is likely to be depleted of values. The Economic Aspect of Geology Most rocks, even dense igneous rocks, are porous in some degree, and certain rocks are porous in a very high degree. The Economic Aspect of Geology It is supposed to have formed by the alteration of olivine and pyroxene in the igneous rocks. The Economic Aspect of Geology All igneous rocks contain at least a trace of barium, which is probably present in the silicates, and these small quantities are the ultimate source of the more concentrated deposits. The Economic Aspect of Geology It is to the igneous rocks that we may look for the original source of the metals of veins. The Elements of Geology Barite itself is not found as an original constituent of igneous rocks or pegmatites, but is apparently always formed by deposition from aqueous solutions. The Economic Aspect of Geology Another type of copper deposits in igneous rocks is the disseminated or "porphyry" deposits. The Economic Aspect of Geology Mineral deposits formed in older geologic periods have in most cases been deeply covered by later sediments and igneous rocks. The Economic Aspect of Geology It is found in veinlets near the surface in altered granites and other igneous rocks. The Economic Aspect of Geology The pre-Cambrian rocks are of very great economic importance, because of their extensive metamorphism and the enormous masses of igneous rock which they involve. The Elements of Geology Sapphire, ruby, emerald, and tourmaline result also from contact metamorphism of sediments in the vicinity of igneous rocks. The Economic Aspect of Geology The term "porphyry" as commonly used includes true porphyries, monzonites, granites, and other igneous rocks. The Economic Aspect of Geology In others, as Mount Hillers, the largest of the group, there is exposed on the summit a core of igneous rock from which the sedimentary rocks of the flanks dip steeply outward in all directions. The Elements of Geology The gneisses appear to be due in many cases to the crushing and shearing of deep-seated igneous rocks, such as granite and gabbro. The Elements of Geology Lavas contain minute percentages of various metallic compounds, and no doubt this was the case also with the igneous rocks which formed the original earth crust. The Elements of Geology The waters which deposit vein stones and ores are commonly hot, and in many cases they have derived their heat from intrusions of igneous rock still uncooled within the crust. The Elements of Geology In this class are included deposits which crystallize within the body of igneous rock, almost, if not quite, simultaneously with the adjacent rock. The Economic Aspect of Geology |
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