andesine


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andesine

[′an·də‚zēn]
(mineralogy)
A plagioclase feldspar with a composition ranging from Ab70 An30 to Ab50 An50, where Ab = NaAlSi3O8 and An = CaAl2Si2O8; it is a primary constituent of intermediate igneous rocks, such as andesites.
References in periodicals archive ?
Plagioclase with andesine to labradorite and clinopyroxene with augitic composition are predominant phases in these volcanic rocks.
Andesine to oligoclase ([An.sub.27-30]) predominate over sodic sanidine and scarce clinopyroxene and titanomagnetite in the matrix of fresh trachyandesite facies.
These data indicate that the plagioclase has An values of 23.02-36.15 and that the granodiorite contains oligoclase (An = 23-28) and andesine (An = 30-36) plagioclase (Fig.
Plagioclase is cloudy to saussuritized in some rocks especially in the more calcic cores but where fresh it is of intermediate anorthite content (calcic oligoclase to andesine).
Tabular plagioclase shows weak zoning with more sodic rim (oligoclase to andesine) and more calcic cores (basic andesine).
In vogesite its composition ranges from andesine to bytownite, and minor albite occurs in the groundmass of monchiquite (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson, 1992).
Other plagioclase grains have distinct cores of higher An content (of andesine composition), which are commonly seriticized (Fig.
Euhedral to subhedral zoned oligoclase to andesine plagioclase (30% to 40%) and anhedral quartz (20% to 30%), in small pods, are the primary constituents of the rock.
Zoned plagioclase with average composition of andesine is the most abundant mineral, with less abundant interstitial K-feldspar and quartz.