anorthoclase


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anorthoclase

[ə′nȯr·thə‚klās]
(mineralogy)
A triclinic alkali feldspar having a chemical composition ranging from Or40 Ab60 to Or10 Ab90 to about 20 mole % An, where Or = KAlSi3O8, Ab = NaAlSi3O8, and An = CaAl2Si2O8. Also known as anorthose; soda microcline.
References in periodicals archive ?
1 samples, with dominating sanidine crystals, anorthoclase glomerocrysts and poikilocrysts (Figure 10).
In thin section (Figure 14) they are classified as vitric and vitric-crystalline flow tuffs (Figure 5) with occasional plagioclase, anorthoclase and sanidine free phenocrysts in a vitroclastic matrix.
with anorthoclase phenocrysts up to 1,5 cm (Figure 15).
all samples have high contents of alkalis (7-10%), in which Na content is greater than K content, which is consistent with anorthoclase, Na-amphibole and Na-Pyroxene crystallization.
On the other hand, anorthoclase poikilocrysts with plagioclase nucleus (Figures 3A and 6F) suggest the following hypothesis (Pardo-Villaveces, 2004): (1) following Carmichael et al.
Those rocks are modal alkaline-feldspar trachytes with anorthoclase and sanidine crystals in the matrix (Pardo, 2004).