Results 221 to 230 of about 19,778 (275)
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Crystallography of Some Lunar Plagioclases
Science, 1970Crystals of calcic bytownite from type B rocks have space group C 1̅ with c ≈ 14 angstroms. Bytownite crystals from type A rocks are more sodic and have space group C 1̅, c ≈ 7 angstroms.
D B, Stewart +3 more
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Oscillatory Zoning in Plagioclase Feldspar
Science, 1980A kinetic mathematical model of crystal growth from the melt is used to describe quantitatively the phenomenon of oscillatory zoning in plagioclase feldspar. In this model, the functional dependence of crystal growth rate on both melt and crystal surface composition and the transport of material within the melt are explicitly considered.
C S, Haase +3 more
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The structures of the plagioclase felspars: VI. Natural intermediate plagioclases
Mineralogical Magazine and Journal of the Mineralogical Society, 1956SummarySpecimens from some forty different localities over the composition range from about 20 % An to about 70 % An have been examined by X-ray single-crystal methods. The majority of these specimens show the normal intermediate plagioclase pattern characterized by weak pairs of subsidiary layer-lines of variable separation. It has been found that the
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The structures of the plagioclase felspars: VII. The heat treatment of intermediate plagioclases
Mineralogical Magazine and Journal of the Mineralogical Society, 1956SummaryPrevious work has established that natural ‘low-temperature’ intermediate plagioclases show single-crystal diffraction patterns in which the subsidiary reflections are split into two; the separation of these split reflections appears to be dependent on the composition of the felspar. Several of these specimens have been subjected to varying heat
P. Gay, M. G. Bown
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Cation Diffusion in Plagioclase Feldspar
Science, 1984Steep compositional gradients in igneous plagioclase feldspar from slowly cooled intrusive bodies imply a maximum value of the intracrystalline diffusion coefficient for NaSi ⇄ CaAl exchange, D max ∼10 -20 centimeters squared per second for temperatures in the range 1250° to 1000°C ...
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Experimental Deformation Of Plagioclases
1970Strength properties and spatial orientation of deformation structures are de-cribed for 11 plagioclases, An2–An95, deformed in compression tests at 25° — 800°C, 5–10 kb confining pressure. At 800°C 10 kb, all single crystals oriented favorably for albite and pericline twin gliding have yield strengths of about 2 kb regardless of composition or ...
I. Y. Borg, H. C. Heard
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Mineralogical Magazine and Journal of the Mineralogical Society, 1934
During the examination of the basalts of Calciferous Sandstone age which are mapped on the one-inch Sheet 23 (Hamilton, Lanarkshire) Scotland, the peculiarities of zoning exhibited by the porphyritic felspar were studied in some detail. As only a summary of the details is possible in the memoir explanatory of the geology of this Sheet, the description ...
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During the examination of the basalts of Calciferous Sandstone age which are mapped on the one-inch Sheet 23 (Hamilton, Lanarkshire) Scotland, the peculiarities of zoning exhibited by the porphyritic felspar were studied in some detail. As only a summary of the details is possible in the memoir explanatory of the geology of this Sheet, the description ...
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On the elimination of plagioclase twinning
Proceedings / Indian Academy of Sciences, 1966A study of the cataclastically deformed plagioclase from a fault zone reveals that the characteristic plagioclase twinning is destroyed in some way. It is presumed that twinning in plagioclase is an irreversible or thermodynamically unstable imperfection.
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The structures of the plagioclase felspars. V. The heat-treatment of lime-rich plagioclases
Mineralogical Magazine and Journal of the Mineralogical Society, 1954This work has been primarily concerned with plagioclase felspars within the composition range Ab30An70 to Ab0An100, i.e. felspars with the anorthite-type structure. Some results for less basic specimens will be quoted where appropriate ; a fuller description of the effects of heat-treatments on intermediate plagioclase felspars will be published later.
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