common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium-sodium) feldspars. Feldspars make up about 60%...

remaining orthoclase with potassium. The resulting intergrowth of the two feldspars is called perthite. The higher-temperature polymorph of KAlSi3O8 is sanidine...

used to describe an intergrowth of two feldspars: a host grain of potassium-rich alkali feldspar (near K-feldspar, KAlSi3O8, in composition) includes exsolved...

anorthite (%An) or albite (%Ab). There are several named plagioclase feldspars that fall between albite and anorthite in the series. The following table...

syenite is trachyte. The feldspar component of syenite is predominantly alkaline in character (usually orthoclase). Plagioclase feldspars may be present in small...

proper checks are done. Feldspar IRSL techniques have the potential to extend the datable range out to a million years as feldspars typically have significantly...

crystalline structure Sanidine, the high-temperature form of potassium feldspar (K,Na)(Si,Al)4O8 Adularia, a more ordered low-temperature variety of orthoclase...

strongly foliated plagioclase-hornblende gneiss and a biotite-hornblende-K-feldspar orthogneiss, which has been intruded by garnet-mica leucogranitic dikes...

consists of regular exsolution layers (lamellae) of different alkali feldspars (orthoclase and sodium-rich plagioclase). Polished moonstones often display...

replacement of alkali feldspar by myrmekite within the enclaves. During this process a reequilibration with the Na-poorer feldspars (plagioclase) in the...

Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most...

type of sandstone containing at least 25% feldspar. Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose...

class of mineral found in the dust, known as K-feldspar, triggers ice formation particularly well. K-feldspar is particularly susceptible to corrosion by...

As another example, the tectosilicate feldspar can be described as a solid solution of the endmembers K-feldspar (KAlSi 3O 8), albite (NaAlSi 3O 8) and...

late Paleozoic continental rifting revealed through thermochronology of K-feldspars, southern Norway" (PDF). Tectonics. 17 (4): 604–620. Bibcode:1998Tecto...

granite rich in the mineral potassium feldspar (K-spar). It is a dense rock with a phaneritic texture. The abundance of K-spar gives the rock a predominant...

feldspars and rock fragments indicate that the rock is an arkose, a subarkose or a lithic arkose, one must then normalize the abundance of feldspars to...

minerals, or olivine, are particularly prone to form mylonites, while feldspar and garnet are resistant to mylonitization. Kyanite Andalusite Sillimanite...

lusters are produced. This effect is most typically produced by adularia, a K-feldspar or orthoclase (KAlSi3O8), from which the name is derived. Adularescence...

authors list (link) Simon & Schuster's Guide to Gems and Precious Stones, K. Lyman, 1996 "Researchers finding applications for tough spinel ceramic"....

Ca-plagioclase feldspars are the first to crystalize out of a melt, after which follows pyroxene, amphibole, biotite, Na-plagioglase, orthoclase feldspar, muscovite...

series is divided into two branches, the continuous (felsic minerals: feldspars) and the discontinuous (mafic minerals). The minerals at the top of the...

micas". They include: Hydro-muscovite with H3O+ along with K in the X site; Illite with a K deficiency in the X site and correspondingly more Si in the...

quartz (β) and low quartz (α). Feldspars are the most abundant group in the Earth's crust, at about 50%. In the feldspars, Al3+ substitutes for Si4+, which...

plagioclase feldspar solid solution series. In pyroclastic rocks in which alkalis predominate over Ca, K-feldspar such as sanidine or albite Na-feldspar are found...

contains several major Sr-bearing minerals including plagioclase feldspar, K-feldspar, hornblende, biotite, and muscovite. Each of these minerals has a...

of primarily feldspar and nepheline. This mixture is higher in alkali and aluminium and typically lower in iron and silica than feldspars from pegmatites...

Fe-edenite), biotite (annite 25%-35%), plagioclase (An3), along with K-feldspar and quartz. (Mafti, 2001). In the Sao Jose do Campestre Massif in Brazil...

little sorting based on grain size and exhibit very little rounding; the feldspars in the rock are relatively fresh in appearance. This lack of sorting and...

billion years old) and for Ribbeck ages were determined with the help of K–Ar dating (~3.3–3.7 billion years) and Uranium/Thorium-Helium dating (~2.3–2...