| 单词 | corundum |
| 例句 | For example apatite is about three times harder than fluorite and diamond is three times harder than corundum. Physical Geology 2015-01-01T00:00:00Z Diamond defines a hardness of 10 and is actually about four times harder than corundum, which is 9. An Introduction to Geology 2017-01-01T00:00:00Z If the quartz can’t scratch the specimen, it might be beryl or corundum, which are harder than quartz. Talking to My Daughter Can Be Harder Than Learning Quantum Mechanics 2021-09-03T04:00:00Z A. Both rubies and sapphires are mostly the same clear mineral: aluminum oxide, in a crystalline form called corundum. From One Mineral, Brilliant Reds and Bright Blues 2018-06-22T04:00:00Z The Bronco mane and eyeball were created from orange sapphires while the head features pave-set diamonds and custom-cut corundum blue stone. Broncos get their Super Bowl rings 2016-06-12T04:00:00Z Some of these minerals may very well be our very own corundum, with its trace elements. The Real Heart of the Ocean 2012-04-14T14:45:05.383Z In its natural state, it is the mineral corundum. Webster's Unabridged Dictionary 2012-03-24T02:00:23.513Z Corundum is a mineral similar to emery, and corundum wheels are made and used in the same manner as emery wheels. Modern Machine-Shop Practice, Volumes I and II 2012-03-23T02:00:33.140Z How to Point a Pencil.—Rub the pencil to a point in the groove of a corundum file. The Evolution of Photography With a Chronological Record of Discoveries, Inventions, etc., Contributions to Photographic Literature, and Personal Reminescences Extending over Forty Years 2012-02-15T03:00:30.577Z Star′-stone, a variety of corundum which, when cut in a particular way, exhibits a reflection of light in the form of a star.—adj. Chambers's Twentieth Century Dictionary (part 4 of 4: S-Z and supplements) 2012-01-30T03:00:19.113Z This crystalline aluminum mineral is called corundum, and people have been wearing it with pride for thousands of years. The Real Heart of the Ocean 2012-04-14T14:45:05.383Z Besides these there may be corundum and carbide of silicon, arising from impurities in the materials employed. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 5 "Gassendi, Pierre" to "Geocentric" 2011-09-02T02:00:20.450Z The emery or corundum wheel is then put on the arbor and tried for being in balance. Modern Machine-Shop Practice, Volumes I and II 2012-03-23T02:00:33.140Z The slag consists of alumina which crystallizes in the forms of corundum and ruby, and is utilized as an abrasive under the name of corubin. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 3 "Frost" to "Fyzabad" 2011-08-15T02:00:28.473Z The Eastern nations have used corundum for this purpose for ages. Inventions in the Century 2011-07-20T02:00:14.643Z In its pure form, corundum is pretty much clear. The Real Heart of the Ocean 2012-04-14T14:45:05.383Z Thus, corundum when pure is colourless, but the presence of traces of certain mineral substances imparts to it not only the red of ruby and the blue of sapphire, but almost every other colour. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 5 "Gassendi, Pierre" to "Geocentric" 2011-09-02T02:00:20.450Z This greater density, be it noted, occurs from the difficulty in mixing the corundum or other abrasive grains with the cementing material with entire uniformity throughout the mass. Modern Machine-Shop Practice, Volumes I and II 2012-03-23T02:00:33.140Z On the Mohs scale, which measures minerals’ hardness from 1 to 10, corundum ranks at 9. Diamonds Not Forever as Royal Kate Leads Way With Sapphire Ring 2011-05-31T04:43:30Z The corundum stone used by the Hindoos and Chinese is composed of corundum powdered, two parts; lac resin, one part. Inventions in the Century 2011-07-20T02:00:14.643Z Chromates were made, the emerald and corundum crystalized, the peridot formed, and many combinations as yet unknown to mineralogists produced. The International Monthly, Volume 4, No. 1, August, 1851 2011-05-18T02:00:11.200Z From his experiments he believes that yellow corundum, or oriental topaz, may have been formed from blue corundum under the influence of radioactive substances present in the soil in which the sapphire was embedded. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 5 "Gassendi, Pierre" to "Geocentric" 2011-09-02T02:00:20.450Z Besides these constituent minerals there are frequently others present, such as the garnets, tourmaline, emerald, sapphire, corundum, etc., which are of economic importance. North America 2011-05-05T02:00:20.027Z Diamonds are a 10 and almost four times harder than corundum. Diamonds Not Forever as Royal Kate Leads Way With Sapphire Ring 2011-05-31T04:43:30Z Under the microscope, it is seen to be a mechanical aggregate of corundum, usually in grains or minute crystals of a bluish colour, with magnetite, which also is granular and crystalline. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z In red corundum the stellate reflexion is less common, and hence the star-ruby occasionally found with the star-sapphire in Ceylon is among the most valued of “fancy stones.” Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 7 "Arundel, Thomas" to "Athens" The oriental amethyst is a rare violet-coloured gem, a variety of alumina or corundum, of much brilliance and beauty. The New Gresham Encyclopedia. Vol. 1 Part 1 A to Amide When corundum presents the bluish tint of typical aquamarine, it is often termed Oriental aquamarine. Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 3 "Apollodorus" to "Aral" Of the less important minerals, Canada is the world’s chief producer of asbestos and corundum. Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 2 "Camorra" to "Cape Colony" The hardness of emery is about 8, whereas that of pure corundum is 9. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z When the radiation is shown by yellow corundum, the stone is called star-topaz. Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 7 "Arundel, Thomas" to "Athens" As found native it is called corundum, when crystallized ruby or sapphire, when amorphous emery. The New Gresham Encyclopedia. Vol. 1 Part 1 A to Amide The mineral occurs as an alteration product of corundum or emery, and is found in granular limestone and other crystalline rocks. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" The mineral has been extensively worked, as at Corundum Hill, Macon county, N.C., near which, in 1871, were discovered numerous rubies, sapphires and pebbles of coarse corundum in the bed of a river. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" The stone known as “Oriental emerald” is a green corundum. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z CHRYSOBERYL, a yellow or green gem-stone, remarkable for its hardness, being exceeded in this respect only by the diamond and corundum. Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 3 "Chitral" to "Cincinnati" Adaman′tine Spar, a name of the mineral corundum or of a brownish variety of it. The New Gresham Encyclopedia. Vol. 1 Part 1 A to Amide Its supplies of the following are inadequate: antimony, asbestos, kaolin, chromate, corundum, garnet, manganese, emery, nitrates, potash, pumice, tungsten, vanadium, zirconium. The Geneva Protocol New South Wales, Queensland and Victoria are other localities for corundum. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" Important deposits of corundum were discovered in Asia Minor by J. Lawrence Smith, when investigating Turkish mineral resources about 1847. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z To polish diamonds they make use of the powder of adamantine spar, or the corundum stone. Travels in China, Containing Descriptions, Observations, and Comparisons, Made and Collected in the Course of a Short Residence at the Imperial Palace of Yuen-Min-Yuen, and on a Subsequent Journey through the Country from Pekin to Canton In conclusion, then, the points to be remembered in determining the origin of corundum gems are four in number. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Emery is an intimate mechanical mixture of corundum, magnetite, and sometimes spinel. The Economic Aspect of Geology Such varieties were termed by J. Black, in consequence of their hardness, adamantine spar, but this name is now usually restricted to a hair-brown corundum, remarkable for a pearly sheen on the basal plane. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" The proportion of corundum in this emery is said to vary from 37 to 57%. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z Another "smell" which is extremely mysterious is that produced by two quartz-pebbles, or even two rock-crystals, or two pebbles of flint or of corundum, when rubbed one against the other. More Science From an Easy Chair When it remotely suggests emerald it is called "Oriental" emerald to denote that it is a corundum gem. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public In North Carolina and Georgia, the corundum occurs in vein-like bodies at the contact of peridotite with gneisses and schists, and also in part in the peridotite itself. The Economic Aspect of Geology Large deposits of corundum exist in the United States, especially in N. Carolina and Georgia, where they are associated with peridotites, often near contact with gneiss. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" In these cells the pulverized enamel is laid and then fused; afterwards it is filed with a corundum file, then smoothed with a pumice stone and polished by means of crocus powder and rouge. Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" 2011-02-06T03:00:53.093Z The most ancient method consisted, in obtaining a flat surface by rubbing or scraping, with corundum or other hard and wearing stone, the stone to be engraved. Scarabs The History, Manufacture and Symbolism of the Scarabæus in Ancient Egypt, Phoenicia, Sardinia, Etruria, etc. Of these minerals the only species that furnishes a fine, deep velvety blue stone is the corundum, and fine specimens of the cornflower blue variety are very much in demand and command high prices. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public 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 Important deposits were discovered by the Geological Survey in 1896, in Hastings county, Ontario; and corundum is now worked there and in Renfrew county. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" We can, however, go far beyond the mere depolishing of glass; indeed I have already said that quartz-sand can wear a hole through corundum. Fragments of science, V. 1-2 Pliny says, corundum was used in the form of a splinter fixed in an iron style. Scarabs The History, Manufacture and Symbolism of the Scarabæus in Ancient Egypt, Phoenicia, Sardinia, Etruria, etc. The yellow corundum rarely has a color that is at all distinctive. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public The domestic production of emery is mainly from New York and Virginia, and corundum comes from North Carolina. The Economic Aspect of Geology Its hardness is generally given as 9, but there are slight variations in different stones, sapphire being rather harder than ruby, and ruby than common corundum. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" The cutting and polishing of the stones is done, as at home, with metal discs and emery or comminuted corundum, which is said to be found in large quantities in the neighbourhood of Canton. The Voyage of the Vega round Asia and Europe, Volume I and Volume II The stones have been rubbed into shape apparently by corundum. Scarabs The History, Manufacture and Symbolism of the Scarabæus in Ancient Egypt, Phoenicia, Sardinia, Etruria, etc. The scientific corundum gems, however, never have these specific defects. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Curtailment of imports during the war greatly stimulated the development of artificial abrasives and their substitution for emery and corundum. The Economic Aspect of Geology The coloured corundums fit for gem-stones come chiefly from Ceylon, Burma, Siam and Montana. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" The surfaces of crystals of corundum are often clouded or dull, whilst its classification of lustre is vitreous. The Chemistry, Properties and Tests of Precious Stones Besides coal, there are in Canada rich deposits of iron ore, lead, nickel, copper, silver, and gold, and the non-metallic minerals include petroleum, asbestos, and corundum. Canada Thus, instead of having a whole series of specific gravities to remember one has only to remember that all the corundum gems have a specific gravity of approximately 4. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Other important abrasives are emery and corundum, garnet, pumice, diamond dust and bort, and feldspar. The Economic Aspect of Geology The coarse corundum, however, is often partially hydrated or otherwise altered, whereby its hardness is diminished. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" Only pretty rocks?—rubies and sapphires were corundum, were pure aluminum oxide! Space Prison This is true whether it has reference to a grindstone, emery, corundum wheel, or a plain oil stone. Practical Mechanics for Boys Spinels, when red, are almost always more yellowish or more purplish than fine corundum rubies. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Emery and corundum are used in various forms for the grinding and polishing of hard materials—steel, glass, stone, etc. The Economic Aspect of Geology Next to diamond, corundum is the hardest known mineral. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" Oats and corundum both came according to prophecy. Lippincott's Magazine, Vol. 22, September, 1878 As the wheel is of emery, corundum or other quickly cutting material, and is always run at a high rate of speed, a great heat is evolved, which is materially increased by pressure. Practical Mechanics for Boys Perhaps the most common of the defects of natural corundum gems is the peculiar appearance known as "silk." A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Production of corundum has come from Canada, South Africa, Madagascar, and India. The Economic Aspect of Geology Coarse dull corundum is found in many localities, and usually has higher commercial value as an abrasive agent than emery, which is less pure. Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 4 "Coquelin" to "Costume" Surely, he thought, this divine draught which they had just begun to taste was not as sweet to her as he found it, or she would not care to talk of oats and corundum. Lippincott's Magazine, Vol. 22, September, 1878 The relatively pure crystals are called corundum, while emery is a variety colored dark gray or black, usually with iron compounds. An Elementary Study of Chemistry No jeweler can afford to risk his reputation for knowledge and for integrity by selling as a natural stone any gem which does not possess the minor defects common to practically all corundum gems. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Diamond is made of carbon; the pearl is calcium carbonate; ruby and sapphire are aluminum oxide—varieties of the mineral corundum; the emerald is silica and alumina, with a minor amount of beryllia. The Economic Aspect of Geology When my companions washed the sands of likely stretches of river beach for fine gold, I examined the waste for corundum crystals, but I found no signs of them. The Hand in the Dark Before the party had time to assemble, the delighted Admiral had himself discovered in his own dish three or four small garnets, one ruby, and several small crystals of corundum. The Lieutenant and Commander Being Autobigraphical Sketches of His Own Career, from Fragments of Voyages and Travels The natural varieties, corundum and emery, are used for cutting and grinding purposes; the purest forms, together with the artificially prepared oxide, are largely used in the preparation of aluminium. An Elementary Study of Chemistry Next after the diamond in hardness come the corundum gems, i. e., ruby, sapphire, and the series of corundum gems of colors other than red and blue. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Alumina is the principal constituent of bauxite, the ore of aluminum, and of the natural abrasives, emery and corundum. The Economic Aspect of Geology It was near the valley that Moynglass found his sample of corundum, with a ruby crystal in it. The Hand in the Dark There is no known substance, not even corundum, hard enough to resist the swift impact of myriads of little stones. Among the Forces Herein also is the kind of corundum known as emery, and esteemed for its polishing properties. How to See the British Museum in Four Visits Thus diamond is a "mineral species," as is also corundum. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public On the higher ground near some small round hills which intercept it, I found the rubies changed into brown corundum. Ceylon; an Account of the Island Physical, Historical, and Topographical with Notices of Its Natural History, Antiquities and Productions, Volume 1 I carried the specimen of corundum in my waistcoat pocket. The Hand in the Dark The amount of raw corundum used annually by the company reaches nearly 1,000 tons. Final Report of the Louisiana Purchase Exposition Commission "Hoe" excavators, pluggers, forceps, pliers, corundum disks and burrs, even the boxwood mallet that Trina was never to use again, all were laid out and ready for immediate use. McTeague There are many different colors of both diamond and corundum, but these different colors are believed to be due to the presence in the pure substance of impurities in small amounts. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public California—nicknamed the "Golden State"—showed among her vast resources gold, silver, platinum, quicksilver, copper, lead, zinc, iron, tin, graphite, crystal, alabaster, corundum, chrysolites, tourmalines, garnets, diamonds, and other gems. By Water to the Columbian Exposition These were, of course, the sapphire, ruby, topaz, amethyst, and other varieties of corundum, the islands evidently containing no emeralds or diamonds. A Strange Discovery In Machinery Hall there was an exhibit comprising a great variety of corundum products, every pound of whose raw material came from Canada. Final Report of the Louisiana Purchase Exposition Commission The corundum burr in McTeague's engine hummed in a prolonged monotone. McTeague Similarly all sapphires, of whatever color, belong to the mineral species "corundum." A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public "Certainly it opens," Mr. Handkin answered, while I trembled with anxiety as he lightly felt it round the edges with fingers engrained with corundum. Erema — My Father's Sin In one of the ruins was a large window made of blue and yellow transparent corundum, in which appeared an inscription made by a setting of rubies. A Strange Discovery 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 McTeague turned, one foot on the pedal of his dental engine, the corundum disk whirling between his fingers. McTeague The variously colored spinels, like the various corundums, all have the same properties, thus they are all of hardness 8 or a little higher, they all have single refraction, and all have specific gravity 3.60. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public The ancient Egyptians besides the hammer, chisel and wedges had tube drills and saws provided with cutting edges of corundum or other hard gritty material. Marvels of Modern Science Among these are gold, silver, copper, lead, iron, mica, corundum, graphite, manganese, kaolin, mill-stone grits, marble, barytes, oil shale, buhrstones, roofing slate, etc. School History of North Carolina : from 1584 to the present time The exhibit showed corundum in bulk, in large wheels, small wheels, hones, and every variety of grinding and sharpening specialties. Final Report of the Louisiana Purchase Exposition Commission Diamonds are pure carbon, but did you know that rubies and sapphires are corundum minerals—rare forms of alumina. Let's Collect Rocks and Shells All corundums other than ruby and blue sapphire are usually called by the term "sapphire," with a qualifying adjective designating the color; thus we may have pink sapphire, golden sapphire, green sapphire, etc. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Examine aluminium, aluminium bronze, corundum, emery, feldspar, argillite, clay. An Introduction to Chemical Science Of some of these minerals, as corundum and mica, North Carolina has already become the chief source of supply. School History of North Carolina : from 1584 to the present time Passing on to the occurrence of the corundum gems we will consider first the ruby. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public When of very fine yellow color the yellow sapphire is sometimes called "Oriental topaz" by jewelers, the term "Oriental" as thus used indicating that the material is corundum. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Leaving the corundum gems we come next to chrysoberyl. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public We also have "Oriental amethyst" and "Oriental emerald" for the purple, and the fine green, and "Oriental aquamarine" for the light blue-green corundum. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public The yellow corundum is also sometimes called "King topaz," especially in Ceylon. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Thus they called blue corundum gems blue rubies; yellow corundums, yellow rubies, etc. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Leaving the naming of the different colors of diamonds we come to the gems furnished us by the mineral known as corundum. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public As was said under ruby, nothing but red corundum should receive that title. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public It should be clearly kept in mind that all these "rubies" are of red corundum, and that in all their distinctive properties except color they are essentially similar. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public It gives one of the best accounts to be had of the history of the artificial production of precious stones, especially of the corundum gems. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public The polishing of stones, whether cabochon or facetted, is accomplished by the use of very finely powdered abrasives such as corundum powder, tripoli, pumice, putty powder, etc. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public It is interesting to note that the corundum gems undergo marked change in color under the influence of radium. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Any of the corundum gems therefore may be used in any type of jewel without undue risk of wear or breakage. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Perhaps Nature, by her slower methods, using the faint traces of radio-active material in the rocks, reddens the corundum of Burmah at her leisure, and finally arrives at the much sought "pigeon blood" color. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Another common type of defect in corundum gems is the occurrence of patches of milky cloudiness within the material. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public There is also a greenish stone that appears reddish by artificial light, which is called scientific alexandrite but which has, however, the composition and properties of the corundum gems rather than those of true alexandrite. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Moreover these defects are characteristic of the corundum gems. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Thus the term ruby should be reserved exclusively for red corundum, and not applied to other red minerals such as garnet, spinel, etc., as is too often done. A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public |
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