A Summary of Progress in Petrography. in 1887-1896 |
From inside the book
Results 1-5 of 12
Page 8
... original mineral . The amphibole in the rocks is pargasite . Two varieties of spinel were ob- served , one a violet and often transparent variety , and the other green pleonast . The violet spinel often accompanies the pargasite and ...
... original mineral . The amphibole in the rocks is pargasite . Two varieties of spinel were ob- served , one a violet and often transparent variety , and the other green pleonast . The violet spinel often accompanies the pargasite and ...
Page 9
... original feldspars have been accentuated , many liquid and gaseous inclosures have been developed in them , and the optical properties of the orthoclase have been changed . Quartz fragments in the altered forms have been surrounded by ...
... original feldspars have been accentuated , many liquid and gaseous inclosures have been developed in them , and the optical properties of the orthoclase have been changed . Quartz fragments in the altered forms have been surrounded by ...
Page 14
... original contact , but one brought about by dislocations . The conclusions of Lévy and Graeff are thus seen to be in accord in some particulars , while in others they are at variance . Fuller discussions are promised later.In the first ...
... original contact , but one brought about by dislocations . The conclusions of Lévy and Graeff are thus seen to be in accord in some particulars , while in others they are at variance . Fuller discussions are promised later.In the first ...
Page 23
... original materials . The cordierite in these rocks is colorless and non - pleochroic , but it becomes brown and pleochroic on heating . It often twins parallel to ∞P , and alters readily to a pinnite - like sub- stance . The other ...
... original materials . The cordierite in these rocks is colorless and non - pleochroic , but it becomes brown and pleochroic on heating . It often twins parallel to ∞P , and alters readily to a pinnite - like sub- stance . The other ...
Page 24
... original rocks , and of the new structures produced in the secondary rocks . The new minerals formed during the production of the schists are albite , microcline , zoisite , garnet , quartz , hornblende , epidote , biotite , muscovite ...
... original rocks , and of the new structures produced in the secondary rocks . The new minerals formed during the production of the schists are albite , microcline , zoisite , garnet , quartz , hornblende , epidote , biotite , muscovite ...
Other editions - View all
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...