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 amphibolite associated Bad Creek basal plane 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 IN UNITED corundum is found corundum occurs corundum-bearing Cowee crystalline Cullasagee decomposed described developed diameter dikes dunite emery feet feldspar fragments garnet Georgia gneiss grains gravel hornblende igneous inch interior veins Jour Laurel Creek limestone localities located Macon County magma magnesia magnetite mass metamorphism mica mica-schist mineral mining Montana Mountain nearly North Carolina observed obtained OCCURRENCE AND DISTRIBUTION occurrence of corundum open cut Origin of corundum outcrops oxide peridotite peridotite formation peridotite rocks plate showing prism quantity Rabun County rhombohedron rubies sapphires saprolitic schist serpentine shaft silicates sparingly specimens spinel stone surface syenite tunnel U. S. Geol variety vary vermiculite vitrified wheel width Yogo zone
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Página 94 - Creek, about 2£ miles northeast of Corundum Hill. 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...
Página 64 - 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 65 - 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 65 - appear to have formed after a great portion of the original corundum had changed into chlorite, as if there had been an excess of alumina ready for combination, which, not finding a supply of the requisite amount of silicic acid and bases, had again crystallized as corundum.
Página 106 - The only two faces that could be identified were the base c(0001) and the rhombohedron #(3032) which is a new face for corundum. On one crystal, two very small faces were observed, which were too small to be measured with the contact goniometer, but were probably the faces of a pyramid of the second order. In determining the rhombohedron, ten or more independent measurements were made of c/^x. These varied from 66° to 68°, but approximated closely to (57°, which agrees very well with the calculated...
Página 78 - 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 124 - The western portion of this State is in the line of peridotites as indicated by the direction of the belt in Georgia and North Carolina, and these rocks are known to exist along the border in the northwestern corner; but no work has been done to trace out their distribution nor to develop the corundum deposits, if such exist.
Página 93 - Figs. 9 and 10, which represent the more common development of these repeated growths, there is but one secondary rhombohedron and base, which sometimes has one of its rhombohedron faces a continuation of one of the rhombohedron faces of the crystal. Figs. 11 and 12...
Página 126 - Appalachain crystalline belt passes under the Cretaceous and later sedimentary formations in the central part of the State near Montgomery. Representatives of the peridotite belt have been found in the vicinity of Dudleyville, in Tallapoosa county, and corundum has been found in fragments on the surface both in this and Coosa, the adjoining county on the west. A little search would doubtless reveal the presence of peridotite, and perhaps also, corundum, to the very borders of the crystalline rocks.