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They consist in great part of feldspars, which vary in composition from anorthite to andesine, or from those kinds in which there is less than one per cent of potash and soda to those in which there is more than seven per cent of these alkalies, the soda preponderating greatly.
This young scientist, too, cherished loving thoughts about Angelina, thoughts of a more earthly and volcanic tinge; certain definite projects which made him forget, at times, his preoccupation with biotite, perlite, magnetite, anorthite, and pyroxene. "Denis," said Keith, in his usual pompous fashion. "Do put down that absurd tray and let people help themselves. Listen to me for a moment.
Tridymite: 100.0 2.3. Orthoclase. Orthoclase. Albite. Oligoclase. Oligoclase. Labradorite. Labradorite. Anorthite. Anorthite. Leucite. Nepheline. Nepheline. Muscovite. Lepidolite. Li 4.85. Biotite. Biotite. Phlogopite. Margarite. Chlorite. Rapidolite. Talc. 63.00 .... .... trace .... 33.60 .... .... W 3.10 2.78. Tremolite. St. Actinolite. Hornblende. Uralite. Augite. Augite. Diallage.
Labradorite, or lime- soda-feldspar, in which the proportions of lime and soda are the reverse to what they are in Oligoclase. 5. Anorthite or lime-feldspar. The two latter feldspars are rarely if ever found to enter into the composition of rocks containing quartz.
Orthoclase is orthoclastic and monoclinic; all the other feldspars are plagioclastic and triclinic. That variety of the Feldspar Group which is called Anorthite has been shown by Rammelsberg to occur in a meteoric stone, and his analysis proves it to be almost identical in its chemical proportions to the same mineral in the lavas of modern volcanoes.
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