Anorthite Thin Section

Cross sections are more or less rectangular.

Anorthite thin section. Biaxial 1 2 a 1 577 b 1 585 g 1 590 d 0 013 2v 78. In thin section plagioclase feldspar grains often look like they re sprinkled with dirt ppl or tiny confetti xpl. High 17 40 ve extreme pinky buff colours occasional.

Anorthite weathers quite readily so it s not terribly abundant on earth. Albite tends to be lighter and anorthite darker. In thin section anorthite is similar to other plagio clase feldspars.

Low moderate negative positive albite anorthite series habit form. You can find the explanation on the plagioclase feldspar page. Plagioclase commonly occurs both as euhedral and anhedral grains.

Colorless frequently cloudy due to incipient alteration pleochroism. Titanite im colourless or pale brown. Anorthite is the calcic end member of the plagioclase feldspar series.

Iron inclusions can produce reds. 20 ucla petrography thin sections 21 www mincryst. Large number of pages viewed.

Crystals are usually tabular parallel to 010 and elongate parallel to the c or a axis. Albite twins if present may be difficult to see in hand specimen. Biaxial or the sign varies depending on composition.