Alkali Feldspar Granite Thin Section

Peppered with minor amounts of black minerals.

Alkali feldspar granite thin section.

This means that biotite in standard thin sections rarely goes completely extinct. In thin section alkali feldspar grains often look like they re sprinkled with dirt ppl or tiny confetti xpl. Earlier workers interpreted the lottah granite as a metasomatised differentiate of the poimena granite. The differences can be subtle and confusing.

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. Most alkali feldspars are compositionally closer to or end member which explains why we often refer to them as k feldspars potassium feldspars. The abundance of k spar gives the rock a predominant pink to reddish hue. Are blue minerals arfvedsonite.

Large number of pages viewed. Cases like that are helpful for learning to tell the feldspars apart. The lottah granite is a composite pluton of tin mineralised strongly peraluminous alkali feldspar granite which intrudes the poimena granite a major component of the mid devonian blue tier batholith of northeastern tasmania. Microcline is a triclinic k feldspar and has a characteristic cross hatched tartan pattern of twinning seen with a petrographic microscope.

It is a dense rock with a phaneritic texture. You can find the explanation on the alkali feldspar page. Orthoclase and sanidine are both optically monoclinic k. 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.

Many rocks have both feldspars like granite. Alkali feldspar also called potassium feldspar or k feldspar has a color range from white to brick red and it s typically opaque. I have the following thin section of 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.

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. Biotite metaluminous granite showing a close up of one crystal.