andesine


Also found in: Dictionary, Wikipedia.

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 ?
Additionally, limited exchange of xenocrysts (labradorite, edenitic amphibole, and bronzite in dacites, oligoclase and andesine in andesitic enclaves) might have occurred during this entrainment stage.
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.
Much of the core shows extensive alteration but microprobe analyses of fresh samples revealed that the plagioclase in both anorthositic and gabbroic rocks has a fairly uniform andesine composition.
Commonly, nearly all the amphibole is blue green and the accompanying plagioclase compositions range from oligoclase to andesine.