A Summary of Progress in Petrography. in 1887-1896 |
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Page 11
... plane are common , the axial ratio was calculated with this as the unit form , and the following result ob- tained : a b c = .83385 : 1 : .58807 . Cleavage is parallel to Po The optical axial plane is oP , with 6 the negative acute ...
... plane are common , the axial ratio was calculated with this as the unit form , and the following result ob- tained : a b c = .83385 : 1 : .58807 . Cleavage is parallel to Po The optical axial plane is oP , with 6 the negative acute ...
Page 14
... planes that show double refraction , are explained as due to the manner of growth . Many new ideas are gathered from the study , one of the most important of which is embodied in a restatement of the law of symmetry of etched figures ...
... planes that show double refraction , are explained as due to the manner of growth . Many new ideas are gathered from the study , one of the most important of which is embodied in a restatement of the law of symmetry of etched figures ...
Page 14
... planes with the greatest capacity for resisting solution . Many more results of interest are contained in the paper , the character of which is sufficiently indicated by the conclusions above referred to . The natural etched figures on ...
... planes with the greatest capacity for resisting solution . Many more results of interest are contained in the paper , the character of which is sufficiently indicated by the conclusions above referred to . The natural etched figures on ...
Page 15
... plane is R , and the forms observed in the individuals are ∞P2 and - 2R . A pseudomorph of aragonite after calcite , from Müsen in Siegen , is one of the few instanesc described in which the latter mineral is known to have changed into ...
... plane is R , and the forms observed in the individuals are ∞P2 and - 2R . A pseudomorph of aragonite after calcite , from Müsen in Siegen , is one of the few instanesc described in which the latter mineral is known to have changed into ...
Page 16
... plane P , determined by Descloizeaux in the Limoges crystals as the ground form . The habit of the Branchville crystals is short pris- matic , with P∞ and various pyramids well developed . The crystals have a good cleavage parallel to ...
... plane P , determined by Descloizeaux in the Limoges crystals as the ground form . The habit of the Branchville crystals is short pris- matic , with P∞ and various pyramids well developed . The crystals have a good cleavage parallel to ...
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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...