Amphibolite Thin Section

Green more rarely brown colourless or blue two cleavages intersect at 120 o pleochroic moderate interference colours inclined extinction typically 30 o common minerals that might be confused with amphibole and may occur in similar rocks.

Amphibolite thin section. Amphiboles may be inexperienced black colorless white yellow blue or brown. At least 50 percent of the mineral grains in schist are aligned this way less than 50 percent makes it gneiss. It is formed by dynamic metamorphism at high temperatures and high pressures that aligns the grains of mica hornblende and other flat or elongated minerals into thin layers or foliation.

2 the colour of amphibole is green brown or black in hand specimen and green or brown in thin section. Home sample of amphibolite coming from massiac auvergne france. Click on the image to enlarge.

It is typically dark colored and dense with a weakly foliated or schistose flaky structure. Schist from the col de l iseran alps. Amphibolite æ m ˈ f ɪ b ə l aɪ t is a metamorphic rock that contains amphibole especially hornblende and actinolite as well as plagioclase.

It can be produced through the metamorphism of mafic igneous rocks such as basalt and gabbro or from the metamorphism of clay rich sedimentary rocks such as marl or graywacke. The content of amphibole and plagioclase together is mostly higher than 90 and may be as low as 75. 2nd cross polarized light.

A1 amphibolite elizabeth johnson. The content of amphibole and plagioclase together is mostly higher than 90 and may be as low as 75. Rock with quartz garnet hornblende muscovite.

The common varieties are tschermakitic and magnesio and ferro hornblende. Amphibolite is a rock of convergent plate boundaries where heat and pressure cause regional metamorphism. Presence of green amphiboles biotite altered to chlorite anomalous bluepolarization colors on the left and altered feldspars.