A Summary of Progress in Petrography. in 1887-1896 |
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Page 10
... structure of several calcareous oölites from Iowa , and of siliceous oölites from Pennsylvania , is represented by Messrs . Barbour and Torrey as concretionary in most cases , while in others the spherules have a brecciated or mosaic ...
... structure of several calcareous oölites from Iowa , and of siliceous oölites from Pennsylvania , is represented by Messrs . Barbour and Torrey as concretionary in most cases , while in others the spherules have a brecciated or mosaic ...
Page 14
... structure , which is described by Mallard as an irregular piling of very small biaxial plates . In this way a high grade of symmetry is imitated , while the plates are really of a low grade . He also adds a nineteenth substance to the ...
... structure , which is described by Mallard as an irregular piling of very small biaxial plates . In this way a high grade of symmetry is imitated , while the plates are really of a low grade . He also adds a nineteenth substance to the ...
Page 18
... structure is lacking . Lamellæ of albite are intergrown with the microcline , but sufficiently large areas of the latter mineral were found to allow of careful measurements of cleavage , angles , etc. The angle between the cleavage ...
... structure is lacking . Lamellæ of albite are intergrown with the microcline , but sufficiently large areas of the latter mineral were found to allow of careful measurements of cleavage , angles , etc. The angle between the cleavage ...
Page 24
... structures produced in the secondary rocks . The new minerals formed during the production of the schists are ... structure is finely worked out , both macro- scopically and microscopically , and the mineral change that accom ...
... structures produced in the secondary rocks . The new minerals formed during the production of the schists are ... structure is finely worked out , both macro- scopically and microscopically , and the mineral change that accom ...
Page
... structure is neither micropegmatitic nor micro- granulitic , though both minerals were deposited simultaneously from the same mother - liquor . He also describes briefly a silicified schist consisting of bands of opal and chalcedony ...
... structure is neither micropegmatitic nor micro- granulitic , though both minerals were deposited simultaneously from the same mother - liquor . He also describes briefly a silicified schist consisting of bands of opal and chalcedony ...
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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...