Plagioclase Feldspar Granite

When a granitoid is devoid or nearly.

Plagioclase feldspar granite.

Rather than referring to a particular mineral with a specific chemical composition plagioclase is a continuous solid solution series more properly known as the plagioclase feldspar series. They are major constituents in a wide range of intrusive and extrusive igneous rocks including granite diorite gabbro rhyolite andesite and basalt. Cloud granite morton gneiss and wausau. This was first shown by the german mineralogist johann friedrich christian hessel 1796 1872 in 1826.

Alkali feldspar granite granite is a medium tocoarse grained acid igneous rock with essential quartz 20 and feldspar where alkali feldspar constitutes between 100 and 35 of the feldspars and minor mafic minerals. The plagioclase feldspar subgroup consists of a continuous mineral series that is arbitrarily subdivided into six mineral categories whose composition varies from being relatively pure sodium aluminum silicate albite to a relatively pure calcium aluminum silicate anorthite. Plagioclase feldspar group minerals are the most common rock forming minerals. Plagioclase is the name of a group of feldspar minerals that form a solid solution series ranging from pure albite na alsi 3 o 8 to pure anorthite ca al 2 si 2 o 8 minerals in this series are a homogenous mixture of albite and anorthite.

Hornblende and biotite are the commonest mafic minerals however muscovite is also frequently encountered. The names of the minerals in the series are arbitrarily given based upon their relative abundance of albite and anorthite. Granite is classified according to the qapf diagram for coarse grained plutonic rocks and is named according to the percentage of quartz alkali feldspar orthoclase sanidine or microcline and plagioclase feldspar on the a q p half of the diagram.