| 单词 | feldspar |
| 例句 | Several of the homes on the way to the quarries were built from huge blocks of granite, containing quartz, feldspar, and mica, all visible to the naked eye, as Fred once showed me. The Line Tender 2019-04-16T00:00:00Z Its heavy concentration of feldspar grains — known as arkose — means the rock is inevitably prone to chemical decay. Hiking along Virginia’s Aquia Creek and finding history a stone’s throw from home 2021-04-01T04:00:00Z But Ergon tiles are porcelain, a mixture of quartz sand, feldspar and clay fired at a very high temperature. The solution for stubborn dirt on porcelain tile? These products, and elbow grease. 2019-07-12T04:00:00Z Porcelain was a most unlikely invention: totally unlike standard pottery, it achieves its amazing toughness and bone-like translucency through an unlikely combination of white clay, feldspar and quartz heated to 1,200C. Stuff Matters by Mark Miodownik – review 2013-07-03T11:15:01Z It is made from a mix of kaolin clay and rocky materials like feldspar, quartz or alabaster, and fired at high temperatures. Art Review: A Jewel Box for Translucent Treasures 2011-12-15T22:59:09Z Originally that would have been feldspar and if you shock that, it turns into maskelynite. Martian meteorite contains pockets of the red planet's atmosphere 2012-02-08T17:40:12Z The materials include Egyptian scarabs, Wedgwood porcelain wafers and blood-red feldspar cylinders flecked with gold. When Form Meets Function: Cuff Links Throughout the Centuries 2016-07-21T04:00:00Z The researchers also used a technique called optically stimulated luminescence to determine when grains of quartz and feldspar in the adjacent sediments were last exposed to sunlight. Earliest Evidence of Wooden Construction Uncovered 2023-09-20T04:00:00Z Luminescence dating normally relies on quartz, but for this study the researchers turned to feldspar, which can absorb much more radioactivity than quartz. Half-million-year-old ‘Lincoln Logs’ may be first wood structure made by ancient humans 2023-09-20T04:00:00Z Their research indicates that the DNA molecules can cling to minerals of feldspar and clay, which protect them from further damage. Oldest Known DNA Paints Picture of a Once-Lush Arctic 2022-12-07T05:00:00Z For example, feldspar is altered — by hydrolysis — to clay minerals. Physical Geology 2015-01-01T00:00:00Z Felsic is the compositional term applied to continental igneous minerals and rocks that contain an abundance of orthoclase feldspar. An Introduction to Geology 2017-01-01T00:00:00Z Many geologists consider it to be the most beautiful rock in all of New England because of its massive feldspar crystals and mica inclusions. The unique challenges of building atop solid rock 2021-07-30T04:00:00Z In 1930 this stone was a 14-foot lump in the Bumpus Quarry in Maine, blocking access to a vast lode of prime feldspar that the quarry owner was eager to mine. Why Geology Is Our Destiny 2021-06-22T04:00:00Z After feldspar, quartz is the most abundant mineral in the Earth's crust. South Africa announces gems found are not diamonds 2021-06-20T04:00:00Z This reaction shows calcium plagioclase feldspar, but similar reactions could also be written for sodium or potassium feldspars. Physical Geology 2015-01-01T00:00:00Z The two different feldspars crystallize out into roughly parallel zones within the crystal, which are seen as these linear markings. An Introduction to Geology 2017-01-01T00:00:00Z Generations of Spruce Pine miners tossed the quartz aside in favor of the feldspar and mica. The special ingredient of those brilliant white sand traps at the Masters 2020-11-11T05:00:00Z It contains lots of pyroxene, olivine and feldspar minerals. Martian meteorite to head home to Red Planet 2020-07-25T04:00:00Z She slid her samples under a microscope, expecting to see the usual quartz and feldspar grains, pollen and random bug parts. From national parks to the deep sea, plastic pollution is showing up wherever scientists look 2020-06-14T04:00:00Z On the weathered surface the feldspar has been altered to the chalky-looking clay mineral kaolinite. Physical Geology 2015-01-01T00:00:00Z As an example, granite is a commonly-used term but has a very specific definition which includes exact quantities of minerals like feldspar and quartz. An Introduction to Geology 2017-01-01T00:00:00Z Like a gold prospector, he used pans to float off less dense quartz and feldspar, and he extracted other unwanted minerals with a magnet. Shock and thaw? Earth’s oldest asteroid impact may have helped lift the planet out of a deep freeze 2019-08-27T04:00:00Z The traps are bunkers, and what appears to patrons and television viewers to be the whitest sand in golf is technically not sand but waste from feldspar mines in North Carolina. Inside the Cultish Dreamworld of Augusta National 2019-06-14T04:00:00Z Optical dating reveals when single grains of quartz or potassium feldspar in a sample of sediment were last exposed to sunlight and, thus, when the sediment was deposited. Mysterious human relatives moved into ‘penthouse’ Siberian cave 100,000 years earlier than thought 2019-01-30T05:00:00Z The schist is relatively weak to begin with, and the feldspar in the sills, which has been altered to clay, makes it even weaker. Physical Geology 2015-01-01T00:00:00Z It usually contains roughly-equal amounts of light and dark minerals, including light grains of plagioclase feldspar and dark minerals like amphibole. An Introduction to Geology 2017-01-01T00:00:00Z Trace elements in the rock’s minerals, which are a granitelike mix of quartz, feldspar, and zircon crystals, provided clues to its origin. Ancient Earth rock found on the moon 2019-01-29T05:00:00Z About 94 percent are stony meteorites, which are composed of the same stuff that’s in beach sand and microchips — silicate minerals like quartz and feldspar. The unlikely story of the meteorite feud that ended up a fugitive from the law 2018-06-25T04:00:00Z The new bunker sand is Spruce Pine feldspar, also used at Augusta National. Risk and Reward: The Transformation of Quail Hollow - Golf Digest 2017-08-03T04:00:00Z Higher than normal rates of weathering of rocks with silicate minerals, especially feldspar, consumes carbon dioxide from the atmosphere and therefore reduces the greenhouse effect, resulting in long-term cooling. Physical Geology 2015-01-01T00:00:00Z Granite commonly has large amounts of salmon pink potassium feldspar and white plagioclase crystals that have visible cleavage planes. An Introduction to Geology 2017-01-01T00:00:00Z The likes of feldspar, quartz and mica will be known by most people. Humans help cook up mineral bounty - BBC News 2017-03-01T05:00:00Z According to the government’s Ministry of Mining Resources, Greenland’s first mines – a feldspar minerals mine and a ruby and pink sapphire mine – are expected to go into production in 2017. The country set to cash in on climate change 2016-12-23T05:00:00Z Below this crispy layer, there is, as in a fresh crème brûlée, a deeper, more pliant level where temperatures are sufficiently high for common minerals like quartz and feldspar to flow plastically as solids. The Quiet Before the Quake 2016-06-09T04:00:00Z It is dominated by quartz, feldspar, clay minerals, iron oxides, and terrestrial organic matter. Physical Geology 2015-01-01T00:00:00Z Diorite is identifiable by it’s Dalmatian-like appearance of black hornblende and biotite and white plagioclase feldspar. An Introduction to Geology 2017-01-01T00:00:00Z Think of feldspar, quartz and mica - these are the ubiquitous species that everyone knows. Earth's rarest minerals catalogued - BBC News 2016-02-13T05:00:00Z The white stuff, he explains, is probably feldspar deposited long after the basalt formed. Notes from the underground 2015-07-19T04:00:00Z Dark, angular crystals of pyroxene floated alongside white, chunky feldspars. Feature: A castaway from ancient Mars 2014-11-25T05:00:00Z The mineral content of soils is variable, but is dominated by clay minerals and quartz, along with minor amounts of feldspar and small fragments of rock. Physical Geology 2015-01-01T00:00:00Z Aluminum concentrates in soils as feldspar and ferromagnesian minerals in igneous and metamorphic rocks undergo chemical weathering processes. An Introduction to Geology 2017-01-01T00:00:00Z An X-ray analysis by CheMin showed that the ground-up rock comprised mostly igneous minerals such as feldspar, pyroxene, olivine and magnetite. Mars Rover Finds Evidence of Ancient Habitability 2013-03-13T19:45:00.600Z The team says the sample contains "significant amounts" of the minerals feldspar, olivine and pyroxene. Martian soil sample 'like Hawaii' 2012-10-31T11:10:03Z Humayun’s team analyzed rock pieces rich in pyroxene and feldspar—minerals that would have been among the first to settle out of a cooling magma chamber. Feature: A castaway from ancient Mars 2014-11-25T05:00:00Z The sand and silt components in this diagram are dominated by quartz, with lesser amounts of feldspar and rock fragments, while the clay component is dominated by the clay minerals. Physical Geology 2015-01-01T00:00:00Z Other commonly found sediment grains include feldspar and lithic fragments. An Introduction to Geology 2017-01-01T00:00:00Z Jake Matijevic was found to be high in elements consistent with the mineral feldspar, such as sodium and potassium, and low in elements such as magnesium and iron. Mars rover finds 'unusual rock' 2012-10-12T09:35:51Z Under a microscope, rounded grains - quartz, feldspar, clam and oyster shells - were visible, along with jagged-edged grains. Tiny remnants of war found in Omaha Beach sand 2012-06-05T16:53:43Z A transparent or translucent variety of common feldspar, or orthoclase, which often shows pearly opalescent reflections; - called by lapidaries moonstone. Webster's Unabridged Dictionary 2012-03-24T02:00:23.513Z At about the point where pyroxene begins to crystallize, plagioclase feldspar also begins to crystallize. Physical Geology 2015-01-01T00:00:00Z The weathering of these rocks — most importantly the hydrolysis of feldspar — has resulted in the consumption of atmospheric carbon dioxide and transfer of the carbon to the oceans and to ocean-floor carbonate minerals. An Introduction to Geology 2017-01-01T00:00:00Z A variety of translucent quartz, spangled throughout with scales of yellow mica. ÷ feldspar, a variety of oligoclase with internal firelike reflections due to the presence of minute crystals, probably of hematite; sunstone. Webster's Unabridged Dictionary (2nd 100 Pages) 2012-03-24T02:00:19.387Z The snowy white feldspar and quartz set off the glittering crystals of hornblende and biotite wonderfully. M lange et Trois: A Trip Across Subduction Zone Madness 2012-03-07T22:15:00.213Z A mineral of the feldspar family, triclinic in crystallization, and in composition a silicate of alumina and soda. Webster's Unabridged Dictionary 2012-03-24T02:00:23.513Z As cooling continues, the various reactions on the discontinuous branch will proceed because silica is abundant, the plagioclase will become increasingly sodium-rich, and eventually potassium feldspar and quartz will form. Physical Geology 2015-01-01T00:00:00Z In fact, feldspar itself is the single most abundant mineral in the Earth’s crust. An Introduction to Geology 2017-01-01T00:00:00Z Even the coves differ in the materials with which their walls are built, feldspar, porphyry, and jasper variegating their rugged features with pleasing effect. Nooks and Corners of the New England Coast 2012-02-22T03:00:25.113Z Granite, gran′it, n. an igneous crystalline rock, composed of grains of quartz, feldspar, and mica, and of a whitish, grayish, or reddish colour.—adj. Chambers's Twentieth Century Dictionary (part 2 of 4: E-M) 2012-01-11T03:00:23.770Z A kind of triclinic feldspar found in the Andes. Webster's Unabridged Dictionary 2012-03-24T02:00:23.513Z At 15 km to 20 km, larger micas form to produce schist, and at 20 km to 25 km amphibole, feldspar, and quartz form to produce gneiss. Physical Geology 2015-01-01T00:00:00Z There are two types of feldspar, one containing potassium and abundant in felsic rocks of the continental crust, and the other with sodium and calcium abundant in the mafic rocks of oceanic crust. An Introduction to Geology 2017-01-01T00:00:00Z The feldspar and porphyry of which the rocks are composed impart a cheerfulness to the walls of these grottoes more pleasing after descending into the gloomy recesses of the south shore. Nooks and Corners of the New England Coast 2012-02-22T03:00:25.113Z Moon′-stone, a variety of feldspar presenting a pearly reflection from within.—adj. Chambers's Twentieth Century Dictionary (part 2 of 4: E-M) 2012-01-11T03:00:23.770Z 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 These include minerals such as quartz, feldspar, mica, amphibole, pyroxene, olivine, and a great variety of clay minerals. Physical Geology 2015-01-01T00:00:00Z Within these frameworks in feldspar are holes and spaces into which other ions like aluminum, potassium, sodium, and calcium can fit giving rise to a variety of mineral compositions and mineral names. An Introduction to Geology 2017-01-01T00:00:00Z This metamorphic bedrock glitters with quartz, feldspar and wine red garnet. City Room: Manhattan Forest, Now Barren, Is Far From Lifeless 2011-12-23T21:20:26Z This granite is composed almost exclusively of reddish feldspar and quartz. Scenes and Andventures in the Semi-Alpine Region of the Ozark Mountains of Missouri and Arkansas 2011-07-10T02:00:18.883Z This consists in great part of Labadorite, or lime feldspar, but has also beds of ordinary gneiss, limestone, and iron ore. The Chain of Life in Geological Time A Sketch of the Origin and Succession of Animals and Plants 2011-06-01T02:00:24.880Z Silica tetrahedra are bonded in three-dimensional frameworks in both the feldspars and quartz. Physical Geology 2015-01-01T00:00:00Z Sandstone that contains feldspar, which weathers more quickly than quartz, is useful for analyzing the local geologic history. An Introduction to Geology 2017-01-01T00:00:00Z Many of the metamorphic terranes consist essentially of quartz, feldspar, and mica, which have been formed by the rearrangement of the mineral matter contained in the rocks during their previous state. North America 2011-05-05T02:00:20.027Z With the two preceding minerals, mica and feldspar, and common quartz, it constitutes the mountain peaks of that remarkable district. Scenes and Andventures in the Semi-Alpine Region of the Ozark Mountains of Missouri and Arkansas 2011-07-10T02:00:18.883Z Columns, pentagonal or heptagonal, crown the tops of hills, and seem rather a composition of hornblende than of augite and feldspar. The Highlands of Ethiopia 2011-02-25T03:01:07.193Z In addition to silica tetrahedra, feldspars include the cations aluminum, potassium, sodium, and calcium in various combinations. Physical Geology 2015-01-01T00:00:00Z Gneiss, a crystalline rock, consisting of quartz, feldspar, and mica. A Manual of the Antiquity of Man 2011-02-21T03:00:07.080Z Mica and feldspar I have not met with. The South-West By a Yankee. In Two Volumes. Volume 2 2011-02-05T03:00:13.817Z The feldspar, which constitutes three-fourths of the mass, is of a dull red hue. Scenes and Andventures in the Semi-Alpine Region of the Ozark Mountains of Missouri and Arkansas 2011-07-10T02:00:18.883Z The trachyte is generally a compact mass of grey feldstein, which contains crystals of glassy feldspar, irregularly embedded, and in different quantities. The Highlands of Ethiopia 2011-02-25T03:01:07.193Z 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 A lot of the remaining dirt is made from the typical components of moon rock, including feldspar and basalt. Moon Not Only Has Water, but Lots of It 2010-10-21T19:37:00Z Many substances are incorporated with soap, such as salt, soda ash, tripoli, crushed volcanic deposits, ground feldspar, infusorial earth of various kinds, silex, etc. Soap-Making Manual A Practical Handbook on the Raw Materials, Their Manipulation, Analysis and Control in the Modern Soap Plant. The great bulk of these granitical formations consists of red feldspar. Scenes and Andventures in the Semi-Alpine Region of the Ozark Mountains of Missouri and Arkansas 2011-07-10T02:00:18.883Z From the general nature of the rocks, it is obvious that the soil consists chiefly of decomposed feldspar, which requires abundance of water. The Highlands of Ethiopia 2011-02-25T03:01:07.193Z Some minerals, like quartz, are virtually unaffected by chemical weathering, while others, like feldspar, are easily altered. Physical Geology 2015-01-01T00:00:00Z Granite , a granular rock consisting of quartz, mica and feldspar,—the material of the original crust of the earth. Unexplored! Some granites which contain hornblende instead of feldspar are desirable. The Future of Road-making in America Where the greenstone becomes porphyritic, the feldspar is a light green. Scenes and Andventures in the Semi-Alpine Region of the Ozark Mountains of Missouri and Arkansas 2011-07-10T02:00:18.883Z Clay and slate are made out of feldspar and mica. Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place On the unweathered surfaces the feldspars are still fresh and glassy-looking. Physical Geology 2015-01-01T00:00:00Z The surface of the ground, so dull and forbidding at first sight, besides being rich in plants, shines and sparkles with crystals: mica, hornblende, feldspar, quartz, tourmaline. My First Summer in the Sierra Gneiss, which is composed of quartz, feldspar, and mica, more or less distinctly slaty, is inferior to granite. The Future of Road-making in America It would no more occur to him that that stone was a displaceable object, and that for the general weal he might displace it, than that its feldspar was of the orthoclase variety. Library of the World's Best literature, Ancient and Modern, Vol. 12 Granite is made of quartz, feldspar, and mica, sometimes with added particles of hornblende. Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place The weathering of these rocks — most importantly the hydrolysis of feldspar — has resulted in consumption of atmospheric carbon dioxide and transfer of the carbon to the oceans and to ocean-floor carbonate minerals. Physical Geology 2015-01-01T00:00:00Z The ice of our winters and of our polar regions is its handiwork, and so equally are the quartz, feldspar, and mica of our rocks. The Voice of Science in Nineteenth-Century Literature Representative Prose and Verse In Book Second, Chapter III, "felspar" was changed to "feldspar". Timar's Two Worlds Thus feldspar, on being pulverized, yields potash; talcose slate yields magnesia; marls yield lime, etc. The Elements of Agriculture A Book for Young Farmers, with Questions Prepared for the Use of Schools Granites differ in colouring because the minerals that compose them, the feldspars, quartzes, micas, and hornblendes, have each so wide a range of colour. Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place In the formation of schist, the temperature has been hot enough so that individual mica crystals are visible, and other mineral crystals, such as quartz, feldspar, or garnet may also be visible. Physical Geology 2015-01-01T00:00:00Z If sienite, very hard, the quartz element predominating, as the feldspar does farther north. The Atlantic Monthly, Volume 15, No. 91, May, 1865 And gardens, where, in the myrrh-sweet June, Magnolias blossom with many a moon Of fragrance; and, in the feldspar light Of August, roses bloom red and white. Weeds by the Wall Verses It contains also numerous veins and beds of hornblend rock and chlorite-schist, and of a peculiar-looking granite, of which the quartz is white as milk, and the feldspar red as blood. My Schools and Schoolmasters or The Story of my Education. The feldspar and mica fragments form clay; the quartz fragments, sand. Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place In the example shown in Figure 7.8d, the dark bands are largely amphibole while the light-coloured bands are feldspar and quartz. Physical Geology 2015-01-01T00:00:00Z Generally the paste consists of a matrix of fine clay tempered with finely pulverized sand, in which may be detected grains of quartz, feldspar, hornblende, augite, particles of iron oxide, &c. Ancient art of the province of Chiriqui, Colombia Sixth Annual Report of the Bureau of Ethnology to the Secretary of the Smithsonian Institution, 1884-1885, Government Printing Office, Washington, 1888, pages 3-188 Lead-coloured compact quartz rock, with imbedded crystals of flesh-coloured feldspar. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island Beneath our feet were slabs of pure white marble and great blocks of greenish feldspar. Across Mongolian Plains A Naturalist's Account of China's 'Great Northwest' A knife will scratch feldspar, as it is not so hard as quartz. Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place Examples of minerals are feldspar, quartz, mica, halite, calcite, and amphibole. Physical Geology 2015-01-01T00:00:00Z Many different kinds of glaze are used, made of ground flint, feldspar, white clay, and other substances. Makers of Many Things Fine-grained gneiss, composed of white quartz, white feldspar, and black mica, with a vein containing hornblend and crystals of feldspar. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island Quartz, he says, being considerably less fusible than feldspar, would naturally consolidate first, and so would give form to the more fusible substance, instead of deriving form from it. The Cruise of the Betsey or, A Summer Ramble Among the Fossiliferous Deposits of the Hebrides. With Rambles of a Geologist or, Ten Thousand Miles Over the Fossiliferous Deposits of Scotland The crystals of feldspar have smooth faces, while quartz breaks with a rough surface as glass does. Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place Cylinder of green feldspar in the British Museum. A History of Art in Chaldæa & Assyria, v. 1 When flint and feldspar are used, they are ground fine at the quarry. Makers of Many Things Very fine-grained gneiss, composed of white quartz, flesh-coloured feldspar, and black mica. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island Similarly opal, moonstone, and turquoise are of about the same hardness as feldspar and are all rated 6. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public The fine mud which now appears as beds of slate was the decay of feldspar and hornblende in the same granite. Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place Sand is composed mainly of particles of quartz or silica, though sometimes feldspar and other minerals are present. The Economic Aspect of Geology It is composed of quartz, feldspar, and mica in varying proportions, and includes several common varieties which mineralogists distinguish scientifically by separate names. The Book of the National Parks Gneiss, composed of yellowish feldspar, white quartz, and black mica. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island The moonstone, being a variety of feldspar, has the pronounced cleavage of that mineral and will not stand blows without exhibiting this property. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Dark particles of feldspar become clay, and may harden into slate. Earth and Sky Every Child Should Know Easy studies of the earth and the stars for any time and place 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 In color granite varies from light gray, when it shines like silver upon the high summits, to warm rose or dark gray, the reds depending upon the proportion of feldspar in its composition. The Book of the National Parks Decomposing fine-grained rock; composed of flesh-coloured feldspar, white quartz, and porcelain clay. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island Moonstone belongs to a species of mineral known as feldspar. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Other grains, which we call feldspar, soften and change into clay, which makes the water muddy as it runs over the rocks. Conservation Reader The associated minerals, mainly quartz and feldspar, are ordinarily present in amounts greater than the mica. The Economic Aspect of Geology Clay is made from crushed rocks, chiefly feldspars. Ontario Teachers' Manuals: Nature Study Greenish-grey slate, containing crystals of white feldspar and specks of hornblend: strata highly inclined, dipping towards the north-east. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island Among the minerals softer than quartz, which are used as gems, we have also "feldspar," which gives us "moonstone," "Labradorite," and "Amazonite." A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Labradorite, the reader may know, is a crystallized feldspar, with traces of other minerals. The Atlantic Monthly, Volume 15, No. 87, January, 1865 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 It occurs in the various feldspars and feldspathic rocks, and in mica. Commercial Geography A Book for High Schools, Commercial Courses, and Business Colleges Fine-grained granite, composed of white quartz, white feldspar, and olive-green mica. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island Sunstone is a feldspar which includes tiny flakes or spangles of some other mineral. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Granite is made of quartz, mica, and feldspar, as has been said before. Diggers in the Earth 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 A few years ago the natives were thrown into a state of the greatest excitement by the discovery of valuable deposits of feldspar on one of their rocky farms. The New England Magazine Volume 1, No. 3, March, 1886 Bay State Monthly Volume 4, No. 3, March, 1886 Breccia, composed of angular and contorted fragments of micaceous schistus, and angular pieces of feldspar and quartz. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island The term has come into such general use, however, that we shall probably have to continue to use it, especially as no other name has come into use for this bluish-green feldspar. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public At Napatuliarasok Island are some lovely specimens of blue and green and golden Labradorite, a striated feldspar with a glorious sheen. A Labrador Doctor The Autobiography of Wilfred Thomason Grenfell The United States also imports some feldspar from Canada. The Economic Aspect of Geology A knob of feldspar, a stunted shrub growing from a crevice, a fault in the rock structure, offered here and there toe-or hand-holds. Oh, You Tex! Fine-grained granite, composed of yellowish feldspar, white quartz, and black mica. Account of a Voyage of Discovery to the West Coast of Corea, and the Great Loo-Choo Island "I do hope I 'll get one with feldspar in it, or something nice and interesting." The Wrong Woman There is also added some more fusible substance, such as feldspar, gypsum, or lime, together with some pure quartz. An Elementary Study of Chemistry The mining of a mica is facilitated by weathering, which softens the associated feldspar, making it an easier task to take out the mica blocks. The Economic Aspect of Geology The coarse-grained friable sandstone, in which the lodges have been excavated, consists chiefly of subangular and rounded grains of quartz and feldspar with a small proportion of black particles. Aboriginal Remains in Verde Valley, Arizona Thirteenth Annual Report of the Bureau of Ethnology to the Secretary of the Smithsonian Institution, 1891-92, Government Printing Office, Washington, 1896, pages 179-262 The maiden's costume consists of a white dress, velvet waist, white flowing sleeves, waist encircled with a crimson sash; hair done up in a neat manner, and decorated with large feldspar beads. Home Pastimes; or Tableaux Vivants Jutting knobs of feldspar and stunted shrubs growing from crevices offered toe-grips instead of the even foothold of the rock shelf. The Yukon Trail A Tale of the North Serpentine, talc, asbestos, and meerschaum are important complex silicates of aluminium and magnesium, and granite is a mechanical mixture of quartz, feldspar, and mica. An Elementary Study of Chemistry Other important abrasives are emery and corundum, garnet, pumice, diamond dust and bort, and feldspar. The Economic Aspect of Geology The matrix has the appearance of a gray speckled quartzite; the angular inclusions being whitish feldspar, with dark-greenish patches of hornblende. Illustrated Catalogue of a Portion of the Collections Made During the Field Season of 1881 Third Annual Report of the Bureau of Ethnology to the Secretary of the Smithsonian Institution, 1881-82, Government Printing Office, Washington, 1884, pages 427-510 Her hair should hang loosely over the shoulders, the head encircled with a string of feldspar or pearl beads. Home Pastimes; or Tableaux Vivants His hand had found a knob of projecting feldspar and he was feeling with his right foot for a hold in some moss that grew in a crevice. The Yukon Trail A Tale of the North If the ore and the limestone do not contain a sufficient amount of silica and aluminium for the formation of the slag, these ingredients are added in the form of sand and feldspar. An Elementary Study of Chemistry As the heading advanced the rock grew steadily softer, the difficult conditions in this locality culminating when a slushy disintegrated feldspar was met, requiring poling and breasting. Transactions of the American Society of Civil Engineers, Vol. LXVIII, Sept. 1910 The New York Tunnel Extension of the Pennsylvania Railroad. The Cross-Town Tunnels. Paper No. 1158 The b�ton pavement of the corridors and balcony is made of annular fragments, facets upward, of black, red, white and slate-colored marbles, feldspar and other stones. Lippincott's Magazine, Vol. 22, August, 1878 It was at this epoch that the rocks called feldspars, syenites, and porphyries appeared. A Journey to the Centre of the Earth Around his neck a string of crystals of feldspar was negligently thrown; and a fetich of white alabaster, representing rudely the form of a panther, depended from the necklace hanging upon his breast. The Delight Makers It contains a large proportion of mica, a small proportion of quartz and still less feldspar, but generally an abundance of iron pyrites in very minute crystals, which, on exposure, are decomposed. The Hudson Three Centuries of History, Romance and Invention These fragments consist of blue quartz, white quartz, and feldspar. History and Comprehensive Description of Loudoun County, Virginia It was made up of quartz, feldspar, and mica, and there were also some isolated specimens of pyrites, hornblend, tourmaline, and serpentine. Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 The New York Tunnel Extension of the Pennsylvania Railroad The Terminal Station - West The cement mills which use feldspar in combination with limestone give off a potash dust, very much to the annoyance of their neighbors. Creative Chemistry Descriptive of Recent Achievements in the Chemical Industries Bracelets of white shells, a necklace of feldspar crystals and turquoises, and strings of yellow cotton threads around her ankles complete the costume. The Delight Makers We must not forget the peculiar changes which such an apparently stable substance as feldspar undergoes when disintegrated and exposed to the chemical action of sea water. Scientific American Supplement, No. 623, December 10, 1887 In these the ophitic arrangement of the coarse feldspars is well defined, and in spite of their subsequent alteration the fragments retain the crystal outlines and polarize together. History and Comprehensive Description of Loudoun County, Virginia One of these beds of basalt was converted into grey syenite by a large granular mixture of white quartz and feldspar with the black hornblende. Rambles and Recollections of an Indian Official Pick up a handful of gravel and you will be able to find much of it feldspar or other mineral containing some ten per cent. of potash. Creative Chemistry Descriptive of Recent Achievements in the Chemical Industries At present the order of crystallization and separation of the mineralogical units seems to have been feldspar, mica, garnet, beryl, quartz. Scientific American Supplement No. 822, October 3, 1891 Composite rocks are definite associations of certain crytonostic, simple minerals, as feldspar, mica, solid silex, augite, and nepheline. COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 This was accompanied by a growth of muscovite and quartz in the unbroken feldspar. History and Comprehensive Description of Loudoun County, Virginia This is a fact which we learn from the nature of feldspar, of which granite is in part composed; this crystallised substance is every where decomposed, where long exposed to the atmosphere. Theory of the Earth, Volume 2 (of 4) The same may be said of all the potash feldspars and mica. Creative Chemistry Descriptive of Recent Achievements in the Chemical Industries The enormous masses of clean feldspar made partially "graphic" by quartz inclosures are a conspicuous feature of the mine. Scientific American Supplement No. 822, October 3, 1891 There was an occasional shelf where, with backs against the wall spotted with crystals of feldspar, they waited to breathe, hardly looking down from the dizzy ledge. Romance Island What little feldspar there was is reduced to quartz and mica, and the quartz pebbles are drawn out into lenses. History and Comprehensive Description of Loudoun County, Virginia At three miles and a quarter we passed on our starboard hand a point of land, which, from the bright colour of the rocks, composed chiefly of feldspar, obtained the name of Red Point. Three Voyages for the Discovery of a Northwest Passage from the Atlantic to the Pacific, and Narrative of an Attempt to Reach the North Pole, Volume 1 In crude specimens, ores of manganese, zinc, copper, nickel, lead, etc., were displayed, as well as feldspar, corundum talc, asbestos, gypsum, and mica. Final Report of the Louisiana Purchase Exposition Commission In one part of the mine, wooden props support an overhanging ledge almost entirely composed of feldspar, which underneath passes into the gray brecciated quartz, which again grades into a white, more compact quartz rock. Scientific American Supplement No. 822, October 3, 1891 The feldspar and the mica, for example, as well as the schorl, are found variously coloured in different granites, and coloured in various proportions. Theory of the Earth, Volume 1 (of 4) The appearance of the rock is not modified by the amount of feldspar which it contains. History and Comprehensive Description of Loudoun County, Virginia The procedure given below applies to silicates undecomposable by acids, of which the mineral feldspar is taken as a typical example. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes Its form is conical, and the rock is composed of basalt feldspar with a small quantity of augite. The Story of the Philippines and Our New Possessions, Including the Ladrones, Hawaii, Cuba and Porto Rico The Eldorado of the Orient The feldspar, the quartz, the mica, have approximately excluded each other, and appear side by side in unmixed purity. Scientific American Supplement No. 822, October 3, 1891 A perfect granite, is, therefore, an extremely hard stone, having quartz and feldspar for its basis; but a perfect whin or basaltes may be extremely soft, so as to cut easily with a knife. Theory of the Earth, Volume 1 (of 4) There is greater variety in texture, from fine aphanitic traps up to coarse grained dolerites with feldspars one-third of an inch long. History and Comprehensive Description of Loudoun County, Virginia For this reason it is best to start with not more than the quantity of the feldspar needed for analysis. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes It is the metallic base of mica, feldspar, slate, and clay. Scientific American Supplement, No. 531, March 6, 1886 It was of porphyritic granite, with distinct crystals of feldspar embedded in a fine grained matrix. Stories from Everybody's Magazine The feldspars are essential constituents of nearly all crystalline rocks, as granite, gneiss, mica, slate, most kinds of basalt and trachyte, etc. The Gutenberg Webster's Unabridged Dictionary Section F, G and H This was materially assisted by the weak lath shapes of the feldspar and the mobility of the micas. History and Comprehensive Description of Loudoun County, Virginia PROCEDURE.—Weigh into platinum crucibles two portions of the ground feldspar of about 0.8 gram each. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes A dark red, finely laminated rock consisting chiefly of decomposed biotite and feldspar, occasional quartz grains and sericite and much iron oxide. The Long Labrador Trail Gypsum is found, especially in Azua province, and the presence of kaolin and feldspar in the province of Santo Domingo, south of the central range, offers a possibility of porcelain manufacture. Santo Domingo A Country with a Future The decomposition of feldspar has yielded a large part of the clay of the soil, also the mineral kaolin, an essential material in the making of fine pottery. The Gutenberg Webster's Unabridged Dictionary Section F, G and H The resulting soil, where not too heavily encumbered with the epidote blocks, is rich and well adapted to farming, on account of the potash and calcium contained in the epidote and feldspar. History and Comprehensive Description of Loudoun County, Virginia A sample of feldspar weighing 1.000 gram is fused and the silica determined. An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes Minerals present are hornblende, biotite, plagioclase, pyroxene, quartz and the alteration products from the feldspar. The Long Labrador Trail The beds of feldspar and flint now being exploited in the Adirondacks will materially help to put this class of potteries on a firmer basis. New York at the Louisiana Purchase Exposition, St. Louis 1904 Report of the New York State Commission "I should explain," said the chemist, "that I have grouped the quartz, feldspar, and mica together, without giving the respective portions of each, because it is evident that the combination represents granite." Jennie Baxter, Journalist It is so named on account of its prominent outcrops in South Mountain, near Weverton, Maryland, and consists entirely of siliceous fragments, mainly quartz and feldspar. History and Comprehensive Description of Loudoun County, Virginia These waters deposited around the spring a brecciated mass of quartz and feldspar, much of it of a reddish color. The Exploring Expedition to the Rocky Mountains, Oregon and California To which is Added a Description of the Physical Geography of California, with Recent Notices of the Gold Region from the Latest and Most Authentic Sources A compact rock of light red color, made up of uniformly rounded grains of quartz, and the feldspar with occasional grain of magnetite. The Long Labrador Trail At some points sulphur had been deposited in crystals, in the midst of the sand and whitish cinders of feldspar which generally precede the eruption of lava. The Mysterious Island The soil is formed of the detritus of the volcanic rocks, specially of feldspar; pumice abounds in the ravines. Narrative of Captivity in Abyssinia with Some Account of the Late Emperor the Late Emperor Theodore, His Country and People The first step in the change was the cracking of the quartz and feldspar crystals and development of muscovite and chlorite in the cracks. History and Comprehensive Description of Loudoun County, Virginia They were, no doubt, pieces of that saussurite jade, or compact feldspar, which we brought home from the Orinoco, and which La Condamine found in abundance at the mouth of the Rio Topayos. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 3 The feldspar is decomposed with the resulting formation of epidote, which is quite prominent. The Long Labrador Trail Potash is also obtainable from feldspar, but I do not know whether any plant has been established for its production from this rock. My Four Years in Germany Most of the broad summit is comparatively level and thick sown with crystals, quartz, mica, hornblende, feldspar, granite, zircon, tourmaline, etc., weathered out and strewn closely and loosely as if they had been sown broadcast. The Yosemite The process consisted of progressive fracture and reduction of the crystals of quartz and feldspar, and was facilitated by the frequent cleavage cracks of the large feldspars. History and Comprehensive Description of Loudoun County, Virginia It is a siliciferous subsulphate of alumina and potash, a compact feldspar, with the addition of sulphuric acid completely formed in it. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 3 The grains of the constituent minerals, quartz, feldspar and magnetite have an angular brecciated appearance; showing uneven extinction and strong crushing effects. The Long Labrador Trail I saw distinctly that, wherever they crossed each other, the veins containing mica and black schorl traversed and drove out of their direction those which contained only white quartz and feldspar. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 It troubled me little at that moment whether feldspar and augite were the two largest components, and I knew that Holman and the two girls were not interested. The White Waterfall This change is a decrease of the feldspar amounting to elimination at the Potomac. History and Comprehensive Description of Loudoun County, Virginia The term contemporary formation is here taken in the sense attached to it by geologists, in speaking of beds of quartz in clay-slate, granular limestone in mica-slate or feldspar in gneiss. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 3 Large and beautiful crystals of feldspar characterise this rock. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 Their basis is greyish blue, rather soft, and showing small white spots which, by the regular form they present, I should conceive to be decomposed feldspar. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 We knew that the place was ugly and sinister, but feldspar and augite didn't give it that look. The White Waterfall As the feldspar, which is granular at the shore, is soon reduced to fine clay and washed away, the direction of its disappearance is the direction of deep water. History and Comprehensive Description of Loudoun County, Virginia "Of course, he is statuary marble, and I'm full of seams and feldspar." The Stillwater Tragedy The porphyries containing vitreous feldspar and hornblende, the phonolite, the greenstone, the amygdaloids, and the basalt, have forms almost as invariable as simple crystallized substances. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 The nature of the phonolites, which are lithoid lavas with a feldspar basis, and the nature of the green slates intermixed with hornblende, oppose this opinion. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 When mica and hornblende are ground up, the result is blue or red clays, as the oxidation of the iron turns the clay red; while the clay made of feldspar is light yellow or white. Ragnarok : the Age of Fire and Gravel The ranges on either side of the glen were generally varieties of gneiss and granite, in many of which feldspar predominated, coarse ferruginous sandstone, and a siliceous rock with mammillary hematite and hornblende. Expedition into Central Australia There are the feldspars, including albite and orthoclase. Let's Collect Rocks and Shells They contain a quantity of vitreous feldspar, of a snow-white colour, and the most brilliant pearly lustre. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 The feldspar intimately mixed with the mass, may be separated into distinct crystals. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 The aluminous minerals contained in granite rocks are feldspar, mica, and hornblende. Ragnarok : the Age of Fire and Gravel Thus he formed, for instance, pumice-stone, feldspar, mica, iron pyrites, &c. artificially. Familiar Letters on Chemistry The feldspar crystals have lost their luster and hardness, and even have decayed to clay. The Elements of Geology At Vesuvius also, we perceive small crystals of vitreous feldspar only in the very ancient lavas of the Somma. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 The feldspar, crystallized in prisms with four unequal sides, about an inch long, passes through every variety of tint from a flesh-red to yellowish white. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 Even quartz was polished and garnets were left projecting upon pedicels of feldspar. Ragnarok : the Age of Fire and Gravel And now the acid, even without heat, dissolves not only the lime, but also so much of the silica of the feldspar as to form a transparent jelly. Familiar Letters on Chemistry In granite regions they contain more or less soda and potash from the decay of feldspar. The Elements of Geology They contain large crystals of feldspar, which are not fissured, and seldom vitreous. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 These ruin-like rocks command the plain; they are composed of a coarse-grained granite, nearly porphyritic, the yellowish white feldspar crystals of which are more than an inch and a half long. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 Mica and hornblende contain considerable oxide of iron, while feldspar has none. Ragnarok : the Age of Fire and Gravel Reaching the rocky wall, I skirted along its base and found it broken by many crevices; above, arose more solid rocks of that feldspar of which the chain of the Alleghanies largely consists. The Master of the World Thus feldspar consists of the insoluble silicate of alumina, together with certain alkaline silicates which are broken up by the action of water containing carbon dioxide, forming alkaline carbonates. The Elements of Geology These masses were the same as the porphyrschiefer of the mountain of Bilin in Bohemia; we recognised in them small long crystals of vitreous feldspar. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 This sandstone contains fragments of quartz, and even of feldspar, cemented by indurated clay. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 Granite is composed of quartz, feldspar, and mica. Ragnarok : the Age of Fire and Gravel The crystals of feldspar appear to have been first formed, leaving between them the space now occupied by the darker-coloured quartz. The Student's Elements of Geology Examining a piece of granite, the most conspicuous crystals which meet the eye are those of feldspar. The Elements of Geology I have found in it neither amphibole nor pyroxene, but some small white points, which seem to be feldspar. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 The crystals of feldspar sometimes preserve externally their reddish-white colour, and rise above the black crust. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 Mica and hornblende generally contain considerable oxide of iron, while feldspar usually yields only a trace or none. Ragnarok : the Age of Fire and Gravel The variety of granite called by the French Pegmatite, which is a mixture of quartz and common feldspar, usually with some small admixture of white silvery mica, often passes into graphic granite. The Student's Elements of Geology Of this structure, called FOLIATION, we may distinguish two types,—a coarser feldspathic type, and a fine type in which other minerals than feldspar predominate. The Elements of Geology The scientific men of the country have made several attempts to calcine this earth, mistaking it for the porcelain earth proceeding from decomposed strata of feldspar. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 These veins, two or three inches thick, are distinguished by a fine-grained quartz-granite crossing a coarse-grained granite almost porphyritic, and abounding in fine crystals of red feldspar. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 To glaze china, it is dipped into a powder of feldspar and SiO2 suspended in water and vinegar, and then fused. An Introduction to Chemical Science When feldspar and mica are also present, it may be called schorly granite. The Student's Elements of Geology GRANITE, as we have learned already, is composed of three minerals,—quartz, feldspar, and mica. The Elements of Geology These balls are composed of lamellar feldspar and hornblende closely commingled. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 It would have been almost impossible to fix the foot on its smooth and sloping surface, if large crystals of feldspar, resisting decomposition, did not stand out from the rock, and furnish points of support. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 Occurrence and Preparation.—Potassium occurs only in combination, chiefly as silicates, in such minerals as feldspar and mica. An Introduction to Chemical Science Werner at least considered syenite as a binary compound of feldspar and hornblende, and regarded quartz as merely one of its occasional minerals. The Student's Elements of Geology SYENITE, composed of feldspar and mica, has consolidated from a less siliceous mixture than has granite. The Elements of Geology The feldspar approximates sometimes to vitreous feldspar when disseminated in very thin laminae in a mass of granular diabasis, decomposed, and emitting a strong argillaceous smell. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 The little fragment which I procured indicated a stratified rock, rich in white feldspar, and containing, together with spangles of mica, grouped in streaks, and variously twisted, some crystals of hornblende. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 Examine aluminium, aluminium bronze, corundum, emery, feldspar, argillite, clay. An Introduction to Chemical Science When the hornblende and feldspar are in nearly equal quantities, and the rock is not slaty, it corresponds in character with the greenstones of the trap family, and has been called "primitive greenstone." The Student's Elements of Geology According to the color of the feldspar the rock may be red, or pink, or gray. The Elements of Geology It is of snowy whiteness, and is no doubt the remains of a decomposed feldspar. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 We saw between Muitaco and the island of Ceiba a hill entirely composed of balls with concentric layers, in which we perceived a close mixture of hornblende and feldspar, with some traces of pyrites. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 Granite is mainly made up of three minerals,—quartz, feldspar, and mica. An Introduction to Chemical Science The two larger prismatic crystals in this drawing represent feldspar, smaller crystals of which are also seen, similar in form, scattered through the base. The Student's Elements of Geology DIORITE, still less siliceous, is composed of hornblende and feldspar,—the latter mineral being of different variety from the feldspar of granite and syenite. The Elements of Geology They contain large nodules of reddish feldspar and but little quartz. Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 1 This tuff appears to the eye nearly pure; but when placed in acid it leaves a considerable residue of sand and broken crystals, apparently of feldspar. Geological Observations on South America Quartz is glassy, mica is in scales, usually white or black, and feldspar is the opaque white or red mineral. An Introduction to Chemical Science In the specimen in Figure 622, the white layers consist almost exclusively of granular feldspar, with here and there a speck of mica and grain of quartz. The Student's Elements of Geology The tiny column of green feldspar ending in the lotus typified eternal youth, even as the carnelian buckle typified the blood of Isis, which washed away all sin. The Spell of Egypt The heat must have been indeed intense which could cause mica to disappear entirely, and feldspar to melt almost completely. Manners and Monuments of Prehistoric Peoples The pebbles are frequently whitewashed and even cemented together by a peculiar, white, friable, aluminous, fusible substance, which I believe is decomposed feldspar. Geological Observations on South America The fibrous radiating structure of the sphaerulites seems, judging from many analogous cases, to connect the concretionary and crystalline forces: the separate crystals, also, of feldspar all lie in the same parallel planes. Volcanic Islands The dark layers are composed of grey quartz and black mica, with occasionally a grain of feldspar intermixed. The Student's Elements of Geology I do not like the look of the rocks half so much as the beef, there is too much of those rather insipid ingredients, mica, quartz and feldspar. More Letters of Charles Darwin — Volume 1 It was made of black, glassy lava mixed with bits of feldspar. Twenty Thousand Leagues Under the Sea The deposition, it may be remarked, of numberless alternations of pure quartz, and of the elements of mica or feldspar does not appear a probable event. Geological Observations on South America The phonolite is of a greenish-grey colour, and is full of minute acicular crystals of feldspar; in most parts it has a conchoidal fracture, and is sonorous, yet it is crenulated with minute air-cavities. Volcanic Islands This mineral, when a section is made at right angles to the alternate plates of feldspar and quartz, presents broken lines, which have been compared to Hebrew characters. The Student's Elements of Geology I am afraid you will tell me to learn my ABC to know quartz from feldspar before I indulge in such speculations. More Letters of Charles Darwin — Volume 1 The soil was largely composed of powdered feldspar; but there were also tracts of gravel shingle, of yellow loam, and of alkaline dust. The Golden Fleece, a romance The prevailing rock is gneiss, often passing, by the disappearance of the quartz and mica, and by the feldspar losing its red colour, into a brilliantly grey primitive greenstone. Geological Observations on South America Small streams of black, basaltic lava, containing olivine and much glassy feldspar, have flowed from many, but not from all of these craters. Volcanic Islands The first of these, gneiss, may be called stratified— or by those who object to that term, foliated— granite, being formed of the same materials as granite, namely, feldspar, quartz, and mica. The Student's Elements of Geology In some places the sulphur had formed crystals among other substances, such as whitish cinders made of an infinity of little feldspar crystals. The Mysterious Island Granite is a compound of feldspar, quartz, and mica, the feldspars being rich in silica, which forms from 60 to 70 per cent of the whole aggregate. The Student's Elements of Geology Not unfrequently quartz and hornblende are arranged in layers in almost amorphous feldspar. Geological Observations on South America The viscidity, which it is now known, that both feldspar and quartz retain at a temperature much below their points of fusion, easily explains their mutual impressment. Volcanic Islands HORNBLENDE-SCHIST is usually black, and composed principally of hornblende, with a variable quantity of feldspar, and sometimes grains of quartz. The Student's Elements of Geology The ordinary granite of Aberdeenshire," says Dr. MacCulloch, "is the usual ternary compound of quartz, feldspar, and mica; though sometimes hornblende is substituted for the mica. The Student's Elements of Geology The same author mentions, that in Shetland a granite composed of hornblende, mica, feldspar, and quartz graduates in an equally perfect manner into basalt. The Student's Elements of Geology In the gneiss, concretions of granular feldspar and others of garnets with mica occur. Geological Observations on South America None of these rocks contain large crystals of feldspar, or have the harsh fracture peculiar to trachyte. Volcanic Islands Both of these alternate with gneiss or mica-schist, or pass into those rocks by the addition of mica, or of feldspar and mica. The Student's Elements of Geology In Hungary there are varieties of trachyte, which, geologically speaking, are of modern origin, in which crystals, not only of mica, but of quartz, are common, together with feldspar and hornblende. The Student's Elements of Geology Orthoclase is orthoclastic and monoclinic; all the other feldspars are plagioclastic and triclinic. The Student's Elements of Geology The prevailing rock has a compact purplish base, with crystals of earthy or opaque feldspar, and often with grains of quartz. Geological Observations on South America These brown-coloured, compact lavas, consist almost entirely of small glimmering scales, or of minute acicular crystals, of feldspar, placed close by the side of each other, and abounding with minute black specks, apparently of hornblende. Volcanic Islands Feldspar, quartz, and mica are usually considered as the minerals essential to granite, the feldspar being most abundant in quantity, and the proportion of quartz exceeding that of mica. The Student's Elements of Geology Next to quartz, which is nearly pure silica or silicic acid, the most important are those silicates commonly classed under the several heads of feldspar, mica, hornblende or augite, and olivine. The Student's Elements of Geology Oligoclase, or soda-lime feldspar, in which soda is present in much larger proportion than lime, and of which mineral andesite are andesine, is considered to be a variety. The Student's Elements of Geology Eighthly, another conformable bed of green porphyry, with specks of green earth and cream-coloured crystals of feldspar. Geological Observations on South America The grey lavas contain numerous, minute, black, easily fusible specks; and but very few large crystals of feldspar. Volcanic Islands This variety is a compound of feldspar and quartz, so arranged as to produce an imperfect laminar structure. The Student's Elements of Geology The two latter feldspars are rarely if ever found to enter into the composition of rocks containing quartz. The Student's Elements of Geology This name has usually been extended to all granular mixtures, whether of hornblende and feldspar, or of augite and feldspar. The Student's Elements of Geology Bed 6, purplish, coarse-grained, hard sandstone, with broken crystals of feldspar and crystallised particles of carbonate of lime; it possesses a slightly nodular structure. Geological Observations on South America It contains numerous crystals of glassy feldspar and black microscopical specks, and is marked with small darker patches, exactly as in the surrounding trachyte. Volcanic Islands Occasionally we find the quartz and feldspar mutually imprinting their forms on each other, affording evidence of the simultaneous crystallisation of both. The Student's Elements of Geology The feldspars which occur in Trachytic rocks are invariably those which contain the largest proportion of silica, or from 60 to 70 per cent of that mineral. The Student's Elements of Geology Through the base are usually disseminated crystals of glassy feldspar, mica, and sometimes hornblende. The Student's Elements of Geology Crystals of feldspar, gradual formation of, at Port Desire. Geological Observations on South America The overlying basaltic lava is in some parts extremely vesicular, in others little so; it is of a black colour, but sometimes contains crystals of glassy feldspar, and seldom much olivine. Volcanic Islands This name has been sometimes given to that variety in which large crystals of common feldspar, sometimes more than three inches in length, are scattered through an ordinary base of granite. The Student's Elements of Geology It rings when struck with the hammer, whence its name; is compact, and usually of a greyish blue or brownish colour; is variable in composition, but almost entirely composed of feldspar. The Student's Elements of Geology This series, about 20,000 feet in thickness, is, as before stated, unconformable to that last mentioned; it consists in great part of gneiss of a reddish tint with orthoclase feldspar. The Student's Elements of Geology There were also some mountains of a porphyry with a brick-red basis, containing irregular, often lens-shaped, patches of compact feldspar, and crystals of feldspar, which latter to my surprise I find to be orthite. Geological Observations on South America Amidst the hillocks composed of these rocks, I found in three places, smooth conical hills of phonolite, abounding with fine crystals of glassy feldspar, and with needles of hornblende. Volcanic Islands One of them, composed of hornblende, mica, feldspar, and quartz, is of a dark colour, and is seen underlying gneiss. The Student's Elements of Geology This trap consists of slaty porphyry and granular feldspar rock, the beds being traversed by joints like those in the associated sandstone, limestone, and shale, and having the same strike and dip. The Student's Elements of Geology The bedded traps consist of feldspar porphyry, and other varieties; and the interposed Llandeilo flags are of sandstone and shale, with trilobites and graptolites. The Student's Elements of Geology At the base of the hill there are syenites, a granular mixture of quartz and feldspar, and harsh quartzose rocks, all belonging to the basal metamorphic series. Geological Observations on South America These more recent lavas are also basaltic, but less compact, and some of them abound with feldspar, so that they even fuse into a pale coloured glass. Volcanic Islands The main body of the granite here is of a porphyritic appearance, with large crystals of feldspar; but in the veins it is fine- grained, and without these large crystals. The Student's Elements of Geology Thus trachyte is usually porphyritic; for in it, as in many modern lavas, there are crystals of feldspar; but in some porphyries the crystals are of augite, olivine, or other minerals. The Student's Elements of Geology The remainder of the mass is quartz, the translucency of which is strongly contrasted to the opaqueness of the white feldspar and black mica. The Student's Elements of Geology Fourthly: a bed, about one hundred feet thick of a compact, partially columnar, pale-grey, feldspathic lava, stained with iron, including very numerous crystals of opaque feldspar, and with some crystallised and disseminated calcareous matter. Geological Observations on South America SECONDLY, a brick-red mass of feldspar, quartz, and small dark patches of a decayed mineral; one minute particle of which I was able to ascertain, by its cleavage, to be hornblende. Volcanic Islands When it alternates with these rocks, it often contains some crystals of mica, and occasionally quartz, feldspar, hornblende, talc, chlorite, garnet, and other minerals. The Student's Elements of Geology They show, nevertheless, that the ingredients were not everywhere exactly the same; and a still greater difference may be traced in the ever-varying proportions of the feldspar, quartz, and mica. The Student's Elements of Geology There are many varieties of trachyte, some of which are highly crystalline, resembling a coarse-grained granite, with large separate crystals of feldspar. The Student's Elements of Geology Some of the varieties appear gradually to become porphyritic with feldspar; and all of them are easily fusible into pale or dark-coloured beads, strongly attracted by the magnet. Geological Observations on South America Close to the granite, the clay-slate is changed into a dark-coloured, laminated rock, having a granular fracture, which is due to imperfect crystals of feldspar, coated by minute, brilliant scales of mica. Volcanic Islands Frequently, between the granite and the hornblende-slate above- mentioned, grains of mica and crystalline feldspar appear in the schist, so that rocks resembling gneiss and mica-schist are produced. The Student's Elements of Geology The quadruple compound of quartz, feldspar, mica, and hornblende, may be termed Syenitic Granite, and forms a passage between the granites and the syenites. The Student's Elements of Geology The purest clay found in nature is porcelain clay, or kaolin, which results from the decomposition of a rock composed of feldspar and quartz, and it is almost always mixed with quartz. The Student's Elements of Geology Eighthly: a bed, about fifty feet thick, of greenish-grey, compact, feldspathic lava, with numerous small crystals of opaque feldspar, black augite, and oxide of iron. Geological Observations on South America Miller, Prof., on ejected Labrador feldspar. -on quartz crystals in obsidian beds. Volcanic Islands The different varieties of rock allied to gneiss, into which feldspar enters as an essential ingredient, will be understood by referring to what was said of granite. The Student's Elements of Geology These rocks possess an extremely varying character; they consist of black, brown, and grey, compact, basaltic bases, with numerous crystals of augite, hornblende, olivine, mica, and sometimes glassy feldspar. Volcanic Islands The feldspar and hornblende in this and the succeeding cases have been determined by the reflecting goniometer, and the quartz by its action under the blowpipe. Volcanic Islands The fragments are angular or rounded, small or large, and consist of bluish or reddish compact feldspathic matter, in which a few acicular crystals of feldspar can sometimes be seen. Geological Observations on South America Obsidian, absent at the Galapagos archipelago. -bombs of. -composition and origin of. -crystals of feldspar sink in. -its irruption from lofty craters. -passage of beds into. -specific gravity of. -streams of. Volcanic Islands Hence some of the slate rocks have become "micaceous; others more indurated, and with the characters of mica-slate and gneiss; while others again appear converted into a hard zoned rock strongly impregnated with feldspar." The Student's Elements of Geology FIRST, a white syenite, streaked and mottled with red; it consists of well- crystallised feldspar, numerous grains of quartz, and brilliant, though small, crystals of hornblende. Volcanic Islands I picked up some specimens, with much glassy feldspar, approaching in character to trachyte. Volcanic Islands The lowest bed is of a pale purple colour, hard, fine-grained, and full of broken crystals of feldspar and scales of mica. Geological Observations on South America |
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