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oligoclase

A triclinic mineral, (Na,Ca)((Si,Al)AlSi2O8) ; plagioclase series of the feldspar group; has NaSi (albite) 10 to 30 mol % and CaAl (anorthite) 90 to 70 mol %; pseudomonoclinic with prismatic cleavage and characteristic polysynthetic twinning commonly visible on cleavage traces; white; may be chatoyant; a common rock-forming 2163 mineral in igneous and metamorphic rocks of intermediate to high silica content; forms the entire mass in some anorthosites; less commonly a vein mineral.

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  • ed.young
  • (Milwaukee, United States)

  •  (V.I.P) 21084 分数
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