Aids in Practical Geology |
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Page 16
... plagioclase felspars , often reveals itself by the appearance of fine alternating duller or more lustrous bands . It is often useful , and in some cases is absolutely necessary , to determine the angles made by certain planes of the ...
... plagioclase felspars , often reveals itself by the appearance of fine alternating duller or more lustrous bands . It is often useful , and in some cases is absolutely necessary , to determine the angles made by certain planes of the ...
Page 138
... Plagioclase in dolerite - Tyne- mouth Dyke , Northumberland . x 14 . Nicols crossed . The crystal has been enlarged by secondary outgrowths into the hemicrystalline groundmass , and the repeated twinning has been exactly reproduced . b ...
... Plagioclase in dolerite - Tyne- mouth Dyke , Northumberland . x 14 . Nicols crossed . The crystal has been enlarged by secondary outgrowths into the hemicrystalline groundmass , and the repeated twinning has been exactly reproduced . b ...
Page 176
... plagioclase from another is a matter requiring considerable care , and the methods should be further studied in the larger text - books . A series of trials with Szabo's system of flame - reactions ( p . 84 ) will often help when the ...
... plagioclase from another is a matter requiring considerable care , and the methods should be further studied in the larger text - books . A series of trials with Szabo's system of flame - reactions ( p . 84 ) will often help when the ...
Page 180
... plagioclase felspar is converted into a scapolite , " Min . Mag . , vol . viii . ( 1889 ) , p . 186 . SERICITE ( see Muscovite ) . Serpentine . Comp.-H. ( Mg , Fe ) , Si , Og . Syst . - Rhombic . I. Soft grey - green , green , black ...
... plagioclase felspar is converted into a scapolite , " Min . Mag . , vol . viii . ( 1889 ) , p . 186 . SERICITE ( see Muscovite ) . Serpentine . Comp.-H. ( Mg , Fe ) , Si , Og . Syst . - Rhombic . I. Soft grey - green , green , black ...
Page 217
... Plagioclase ( Albite or Oligo- clase ) . I. The clear glassy granules of the quartz , devoid of cleavage , are easily distinguished ; muscovite may be present , though rarer than dark micas ; the dull edges of biotite crystals often ...
... Plagioclase ( Albite or Oligo- clase ) . I. The clear glassy granules of the quartz , devoid of cleavage , are easily distinguished ; muscovite may be present , though rarer than dark micas ; the dull edges of biotite crystals often ...
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Common terms and phrases
acid altered ambulacral andesites angles aperture appear areas assay augite axis basal bead become biotite brown calcareous calcite carbonate Carboniferous character CHARLES GRIFFIN cleavage colour colourless common commonly constituents convex Cretaceous crossed nicols crystalline crystals developed Devonian EDITION Engineer eurites examined EXETER STREET fairly felspar flame foliated fossils fragments genera Geol glass Gotlandian grains granite granular granules green groundmass Handsome Cloth head-shield hinge-line hornblende igneous rocks iron Jurassic lavas leucite limestones lobes magnetite margin marked mass mica microscope minerals mouth numerous observed occur olivine opaque ophitic optic ordinary Ordovician orthoclase outer oxide parallel Plagioclase planes plates pleochroism polarised porphyritic posterior powder PRACTICAL prisms Prof pygidium pyroxene quartz radial reaction Refr refractive rhyolites ribs rotation sections seen septa shell side silica soda sometimes specific gravity specimens spherulites structure sulphur surface Suture-lines trace trachytic tube types typical umbo valve ventral whorl