A Summary of Progress in Petrography. in 1887-1896 |
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Page 8
... minerals . One variety of the humite occurs in rounded crystals of a clear yellow color , that become ... mineral . The amphibole in the rocks is pargasite . Two varieties of spinel were ob- served , one a violet and often ...
... minerals . One variety of the humite occurs in rounded crystals of a clear yellow color , that become ... mineral . The amphibole in the rocks is pargasite . Two varieties of spinel were ob- served , one a violet and often ...
Page 9
... minerals developed in the surrounding rock by the solution of the inclusion are spinel , hypersthene , and sometimes labra- dorite , sometimes forming holocrystalline aggregates , and at other times occurring as individual grains bathed ...
... minerals developed in the surrounding rock by the solution of the inclusion are spinel , hypersthene , and sometimes labra- dorite , sometimes forming holocrystalline aggregates , and at other times occurring as individual grains bathed ...
Page 10
... Minerals . - Castanite , associated with barite occurs on a copiapite specimen from Sierra Gordo , Chili , in the ... mineral is light gray and transparent . On its exterior it is covered with an opaque coating of brown manganese ...
... Minerals . - Castanite , associated with barite occurs on a copiapite specimen from Sierra Gordo , Chili , in the ... mineral is light gray and transparent . On its exterior it is covered with an opaque coating of brown manganese ...
Page 11
... mineral agrees well with the view that it is closely allied to pectolite . Its axial plane is Poo , with the acute bisectrix . The double refraction is positive , and the dispersion is strong s > p . - Pinakiolite and trimerite are both ...
... mineral agrees well with the view that it is closely allied to pectolite . Its axial plane is Poo , with the acute bisectrix . The double refraction is positive , and the dispersion is strong s > p . - Pinakiolite and trimerite are both ...
Page 12
... mineral thus obtained are bounded by tetrahe- drons , octahedrons , and other forms apparently belonging to the ... minerals formed by heating some specimens to a temperature beyond which they lose water , occasionally examining ...
... mineral thus obtained are bounded by tetrahe- drons , octahedrons , and other forms apparently belonging to the ... minerals formed by heating some specimens to a temperature beyond which they lose water , occasionally examining ...
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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...