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A plagioclase feldspar mineral with a composition ranging from Ab90 An10 to Ab70 An30, where Ab = NaAlSi3O8 and An = CaAl2O8.



a rock-forming mineral of the feldspar (plagio-clase) group; an isomorphous mixture of 10–30 percent anorth-ite, Ca[Al2Si2O8], and 70–90 percent albite, Na[AlSi3O8].

References in periodicals archive ?
In thin section (Figure 16) some of these phenocrysts are pokilocrysts with an oligoclase nucleus (Figure 16 B).
Under different nucleation, diffusion and growing rates, augite-aegirine, sphene, zircon, oligoclase, anorthoclase and sanidine could crystallize in the intratelluric environment.
Normally zoned plagioclase phenocrysts are oligoclase on average ([An.
The Sedgwick Granite is a grey, medium- to coarse-grained, equigranular, biotite granite that contains 35% microcline, 32% quartz, 28% oligoclase, 4% biotite, and trace amounts of zircon, apatite, and titanite.