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Feldspars make up about 60% of the Earth's crust [3] and 41% of the Earth's continental crust by weight. [5] [6] Feldspars crystallize from magma as both intrusive and extrusive igneous rocks [7] and are also present in many types of metamorphic rock. [8] Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. [9]
Alkali feldspar granite, some varieties of which are called 'red granite', [1] is a felsic igneous rock and a type of 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 pink to reddish hue; peppered with minor amounts of black minerals. [2] [3]
Orthoclase, or orthoclase feldspar (endmember formula K Al Si 3 O 8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for "straight fracture", because its two cleavage planes are at right angles to each other. It is a type of potassium feldspar, also known as K-feldspar.
Potassium feldspar refers to a number of minerals in the feldspar group that contain large amounts of potassium in the crystal lattice. Orthoclase (endmember formula K Al Si 3 O 8), an important tectosilicate mineral that forms igneous rock; Microcline, chemically the same as orthoclase, but with a different crystalline structure
Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. [1] The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known.
Pyroxene and feldspar are the major minerals in basalt, andesite, and gabbro rocks. [1] [2] Structure. ... a green variety of spodumene. Rhodonite; Wollastonite;
Moonstone is a sodium potassium aluminium silicate ((Na,K)AlSi 3 O 8) of the feldspar group that displays a pearly and opalescent schiller. [ 1 ] [ 2 ] An alternative name for moonstone is hecatolite [ 2 ] (from goddess Hecate ).
The two types of feldspar are usually: plagioclase: a member of the anorthite-albite series (CaAl 2 Si 2 O 8-NaAlSi 3 O 8) alkali feldspar: a member of the orthoclase-albite series (KAlSi 3 O 8-NaAlSi 3 O 8). In fact ternary feldspars (comprising albite+orthoclase+anorthite) are believed to have been present in the high temperature state of the ...