A Summary of Progress in Petrography. in 1887-1896 |
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Page 10
... silica content from the surrounding rock , it is easily destroyed , merely traces of it remaining to mark its former presence.Gray- wacke in contact with granite in the Lausitz , Saxony , is changed to knotty ( Knoten ) graywackes , in ...
... silica content from the surrounding rock , it is easily destroyed , merely traces of it remaining to mark its former presence.Gray- wacke in contact with granite in the Lausitz , Saxony , is changed to knotty ( Knoten ) graywackes , in ...
Page 11
... silica and water , the formula becomes R , BMnO ,, or a manganese ludwigite . The black , lustrous crystals are usually ortho rhombic , rectangular tables , in which the brachypinacoid is most developed . In addition to this there is ...
... silica and water , the formula becomes R , BMnO ,, or a manganese ludwigite . The black , lustrous crystals are usually ortho rhombic , rectangular tables , in which the brachypinacoid is most developed . In addition to this there is ...
Page 12
... silica , according to Vernadsky , 10 unite at a white heat to form a glass which , under the microscope , is seen to be filled with little needles of sillimanite , with the composition : SiO , = 37.31 ; Al , O , 63.65 . Por- celaine ...
... silica , according to Vernadsky , 10 unite at a white heat to form a glass which , under the microscope , is seen to be filled with little needles of sillimanite , with the composition : SiO , = 37.31 ; Al , O , 63.65 . Por- celaine ...
Page 13
... silica in the silicic - acid portion of the combination . The author determines incidentally the solubility of several of the zeolites in different solvents , and concludes his paper with a table giving the supposed composition of the ...
... silica in the silicic - acid portion of the combination . The author determines incidentally the solubility of several of the zeolites in different solvents , and concludes his paper with a table giving the supposed composition of the ...
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Common terms and phrases
acid Al,O alteration Amer AMERICAN NATURALIST analysis andalusite angle aragonite augite axial ratio basalts beryl biotite brucite Bull calcite calcium chlorite cleavage Colby University color colorless composition constituents containing cordierite corresponding crystalline crystals density described diabase double refraction dyke eruptive rocks Fe,O Fe₂O feldspar FeO MgO CaO FeO MnO forms formula Franc gabbro-diorites gabbros garnet Genth gneisses granite granulites ground-mass H₂O habit hexagonal hornblende humite hypersthene imbedded inclusions Jour Kryst leucite masses melanophlogite metacinnabarite mica mineral MINERALOGY AND PETROGRAPHY.¹ Mitth molecules muscovite Neues Jahrb nosean occur olivine optical original orthoclase ottrelite parallel Penfield Petrog PETROGRAPHY.¹ Petrographical phenacite plagioclase plane plates polymorphism prismatic produced pseudomorphs pyroxene quartz regarded rock individual Rosenbusch schistose schists serpentine silica sodium soluble specific gravity specimens spinel structure substance sulphur symmetry tabular temperature tonalite tourmaline twinned varieties W. S. Bayley Waterville yielded Zeits zircon zone
Popular passages
Page 19 - The plane of the optical axes is perpendicular to the plane of symmetry, and makes with c an angle of °7 in acute /9. A = b. 2H na = 104° 27'.
Page 14 - The larger part of the dust is thought to be a sediment from the air, and to have been obtained by it from a region of crystalline schists. The chondri, on the other hand, are thought to be of cosmic origin, since they are similar to the chondri obtained in deep-sea soundings. If the amount of the dust collected from the snow in Greenland represents the fall of one year, the total amount falling upon the entire surface of the earth in this time is 125 million kilograms, equivalent to a cube of thirty-one...
Page 14 - Wiilfing 21 for investigation, by whom it has been found to consist in greater part of feldspar, quartz, mica, and hornblende. There are present in it also garnet, zircon, magnetite, augite, and sillimanite, and with them is mixed a nitrogenous organic substance. The most interesting constituents of the dust...