Corundum and Its Occurrence and Distribution in the United States: (a Rev. and Enl. Ed. of Bulletin No. 180)U.S. Government Printing Office, 1906 - 175 páginas |
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Términos y frases comunes
abrasive Alteration product alumina amphibole amphibolite basal plane basic magnesian rocks belt biotite blue border vein Buck Creek Bull Chester chlorite chromite Clay County color corun corundum corundum crystals corundum deposits corundum gems Corundum Hill corundum is found corundum occurs corundum-bearing Cowee crystals of corundum cyanite decomposed described developed dikes dunite emery feet feldspar found associated garnet Georgia gneiss grains granite gravels hornblende igneous interior veins Jackson County Jour Laurel Creek limestone localities Macon County magma magnesia magnetite masses of corundum metamorphism mica mica-schist mining molten Mountain muscovite nearly nodules norite North Carolina observed obtained occurrence of corundum outcrops oxide peridotite peridotite formation peridotite rocks plagioclase portion prism pyroxenite quantity quartz rhombohedron River Rock constituent rubies sapphires saprolitic schists separated serpentine shaft silicates similar sparingly specimens spinel surface Survey syenite U. S. Geol vary vermiculite vicinity width zone
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Página 175 - Nature and origin of deposits of phosphate of lime, by RAF Penrose, jr., with introduction by NS Shaler. 1888. 143 pp. (Out of stock.) B 65. Stratigraphy of the bituminous coal field of Pennsylvania, Ohio, and West Virginia, by IC White. 1891. 212 pp., 11 pis. (Out of stock.) Bill.
Página 102 - Some good ruby corundum occurs here, together with a peculiar brown or bronze variety, known locally as " pearl corundum," which shows distinct asterism, both by natural and artificial light, when the stone is cut en cabochon. In natural light these corundums all show a bronze luster and are somewhat similar to the cat's-eye, but in artificial light the star is more distinct. Most of the bronze corundum is in rough crystals, but some have been found that have the prismatic faces smooth and well developed,...
Página 57 - Green, scaly chlorite is almost the only constituent of these rocks, though sometimes they are necked with small white grains of feldspar, and occasionly amphibole needles are seen. The chlorite is in small scales, never very coarse, as is sometimes the case in the zones about peridotite, and often they are so minute as to impart quite a compact appearance to the rock. In one of these belts, on Caney Fork of Tuckaseegee river, corundum is disseminated through the chlorite in small rounded masses,...
Página 75 - He calls attention to the occurrence of corundum chiefly in chlorite veins and says " the chlorite seems to have been first crystallized, and then, the alumina of which the corundum is composed was evidently in a state of solution and must have permeated the chlorite either in thermal waters or steam.
Página 74 - Shepard* in an extended article on the corundum of North Carolina and Georgia, describes the occurrences of corundum and chrysolite, the associated minerals and what he calls the development of the "Strata" which "exhibit the following order of formations: 1. Chrysolitic rock somewhat mixed with anthophyllite ; 2. a layer of micaceous rock; 3. a seam of chalcedony ; 4. a stratum of chloritic rock (ripidolite) ; 5. the same through which the corundum is regularly diffused, sometimes in narrow veins...
Página 75 - That, at the great period when the chromiferous chrysolite beds (in part subsequently altered into serpentine, etc.) were deposited, a large quantity of alumina was separated which formed beds of corundum...
Página 88 - From what has been observed in nature and from the experiments that have been made in the laboratory, it seems that the separation of alumina as corundum from molten magmas is dependent upon the composition of the chemical compounds that are the basis of the magma, upon the oxides that are dissolved with the alumina in the magma and upon the amount of alumina itself.
Página 33 - Transylvania counties, a pyroxenite composed of interlocking, coarse-bladed, gray enstatite constitutes an important part of the outcrop; and at a number of places the pyroxenite alone forms oval and lenticular masses in every way similar to those composed of peridotite. In both cases corundum-bearing zones of secondary minerals are frequently formed along the borders of the pyroxenite and intersect the mass of the rock in exactly the same manner as described above for peridolite.
Página 104 - ... stones have been cut, have been found here in the gravels of the stream, together with blue and yellow corundum of gem quality. By following up the gravels the corundum was located in a small vein in the decomposed peridotite. At the Sapphire and Whitewater mines, near Sapphire, fragments of corundum of a fine blue color have been found, from which small but good gems have been cut. Quite large amounts of commercial corundum have been taken out at the Bad Creek and Socrates mines, and also at...