alkali feldspar


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Related to alkali feldspar: Plagioclase feldspar, quartz, hornblende, K feldspar

alkali feldspar

[′al·kə‚lī ′feld‚spar]
(mineralogy)
A feldspar composed of potassium feldspar and sodium feldspar, such as orthoclase, microcline, albite, and anorthoclase; all are considered alkali-rich.
References in periodicals archive ?
It consists mainly of perthitic alkali feldspar and quartz, and mafic minerals are less abundant than in the quartz alkali-feldspar syenite to alkali-feldspar syenite (Fig.
The degree of porosity depends on the composition of the parent feldspar grain, with plagioclase producing a dense clay matrix and alkali feldspar a highly porous clay matrix.
Albite and alkali feldspar are absent in the groundmass in which the only feldspar is plagioclase in the andesine-labradorite range, indicating that the megacrysts are xenocrysts rather than phenocrysts.
Plagioclase is often replaced by alkali feldspar and varies in composition from andesine to oligoclase.
The evolution of the trachyte in the melt phase involved crystallization of feldspars, clinopyroxene, and Fe-Ti oxides, whereas the evolution of the rhyolite was dominated by crystallization and fractionation of alkali feldspar.
Plagioclase dramatically removes Sr at intermediate stages and alkali feldspars sequester Ba and Rb as late-stage trachytes and phonolites form in alkaline magmas.
1987, Determining (Al,Si) distribution and strain in alkali feldspars using lattice parameters and diffraction-peak positions: A review, American Mineralogist, v.
The study of the efficiency of (optical) response by stimulation means the measurements of the OSL stimulation spectra of quartz and alkali feldspars in the widest possible spectral region.