A Summary of Progress in Petrography. in 1887-1896 |
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Page 10
... composition as the enclosing rock , the former have in general been well preserved . If , on the contrary , the inclusion differs in its silica content from the surrounding rock , it is easily destroyed , merely traces of it remaining ...
... composition as the enclosing rock , the former have in general been well preserved . If , on the contrary , the inclusion differs in its silica content from the surrounding rock , it is easily destroyed , merely traces of it remaining ...
Page 11
... composition : Sio , 39.77 BeO 17.08 MnO 26.86 : FeO CaO 3.87 12.44 MgO .61 corresponds to ( Mn Be ) SiO ,, a manganese phenacite . The trans- parent bright red crystals have an hexagonal habit , due to twinning of triclinic individuals ...
... composition : Sio , 39.77 BeO 17.08 MnO 26.86 : FeO CaO 3.87 12.44 MgO .61 corresponds to ( Mn Be ) SiO ,, a manganese phenacite . The trans- parent bright red crystals have an hexagonal habit , due to twinning of triclinic individuals ...
Page 12
... composition : SiO , = 37.31 ; Al , O , 63.65 . Por- celaine consists essentially of the same substances , viz . , a glass holding acicular crystals of sillimanite . - Many of the most important zeolites have been manufactured by Doelter ...
... composition : SiO , = 37.31 ; Al , O , 63.65 . Por- celaine consists essentially of the same substances , viz . , a glass holding acicular crystals of sillimanite . - Many of the most important zeolites have been manufactured by Doelter ...
Page 13
... composition of the members of the group . Heulandite is represented as CaAl , Si , O ,, + 2H , SiO , + 3Aq ; natrolite as Na , Al , Si , O , + H , SiO ,, etc. - Messrs . C. and G. Friedel , 12 by the action of lime on mica in the ...
... composition of the members of the group . Heulandite is represented as CaAl , Si , O ,, + 2H , SiO , + 3Aq ; natrolite as Na , Al , Si , O , + H , SiO ,, etc. - Messrs . C. and G. Friedel , 12 by the action of lime on mica in the ...
Page 14
... composition R , " R , " ( SiO , ) ,, and the series of the alkaline garnets . The etched figures on the latter indicate that they are all tetrahedrally hemihedral , and a discussion of the best analysis of them leads to the conclusion ...
... composition R , " R , " ( SiO , ) ,, and the series of the alkaline garnets . The etched figures on the latter indicate that they are all tetrahedrally hemihedral , and a discussion of the best analysis of them leads to the conclusion ...
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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...