Alkali feldspar granite Alkali feldspar granite Alkali feldspar granite, some varieties of which are called 'red granite', 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. As shown in the QAPF diagram, alkali feldspar granite contains between 20% - 60% quartz. Less quartz content would lead to "quartz alkali feldspar syenite". More than 90% of the total feldspar content is in the form of alkali feldspar.
A-type granite A-type granite A-type granites are a class of granite. They are characterised by low water and a lack of tectonic fabric. A stands for anorogenic or anhydrous. The granite class was proposed by Loiselle and Wones in 1979. It was in addition to I-, S- and M-type granites. The A-type granites form in an extensional tectonic setting. This could either be far from any orogeny, or after orogeny is completed. Chemical characteristics of A-type granites include high silica, alkalis, zirconium, niobium, gallium, yttrium and cerium. The ratio of gallium to aluminium is high, as is the ratio of iron to