Alkali Feldspar Granite Thin Section

Microcline is a regular and essential ingredient of sandstone especially feldspar arenaceous rocks and feldspar graywacke sections 5 5 3 2 and 5 5 3 3 section 5 5 3 2 section 5 5 3 3.

Alkali feldspar granite thin section. The differences can be subtle and confusing. This means that biotite in standard thin sections rarely goes completely extinct. Cases like that are helpful for learning to tell the feldspars apart. Microcline is a triclinic k feldspar and has a characteristic cross hatched tartan pattern of twinning seen with a petrographic microscope.

You can find the explanation on the alkali feldspar page. The abundance of k spar gives the rock a predominant pink to reddish hue. Large number of pages viewed. Most alkali feldspars are compositionally closer to or end member which explains why we often refer to them as k feldspars potassium feldspars.

Biotite metaluminous granite showing a close up of one crystal. In thin section alkali feldspar grains often look like they re sprinkled with dirt ppl or tiny confetti xpl. Alkali feldspar also called potassium feldspar or k feldspar has a color range from white to brick red and it s typically opaque. Earlier workers interpreted the lottah granite as a metasomatised differentiate of the poimena granite.

Anorthoclase na k alsi 3 o 8 is a crystalline solid solution in the alkali feldspar series in which the sodium aluminum silicate member exists in larger. As any feldspar cools below the solidus its isopleth eventually intersects the convex upward solvus below which the single feldspar unmixes or exsolves under equilibrium conditions into two stable alkali feldspar solid solutions. Many rocks have both feldspars like 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.

Peppered with minor amounts of black minerals. At ph 2 o 200 mpa any feldspar precipitated from a melt is a homogeneous alkali feldspar solid solution. Orthoclase is frequently known as potassium feldspar or k spar and is easily distinguished from the plagioclase feldspars in hand sample by its lack of striations. I have the following thin section of alkali feldspar granite.

It is a dense rock with a phaneritic texture. Are blue minerals arfvedsonite.