Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations. • Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology.

This sample is a coarse grained two pyroxene gabbro. Minerals present are plagioclase (labradorite), orthopyroxene, augite and accessory opaques. Note the rectangular outlines of plagioclase - an igneous texture, which is quite different from the metamorphic 'granoblastic' texture in the two pyroxene granulite which is made from the same three ...

2023年4月23日 · Pyroxene is a set of essential rock-forming inosilicate minerals discovered in many igneous and metamorphic rocks. Pyroxenes have the general components is XY (Si,Al)2O6. Although aluminium substitutes extensively for silicon in silicates consisting of feldspars and amphiboles, the substitution occurs only to a confined extent in most pyroxenes.

The top two photomicrographs show the weak pale green pleochroism of Clinopyroxene. The bottom photomicrograph shows that even though the cleavage planes are vertical (aligned N-S), the crystal is still in illumination under cross polarized light.

Igneous and metamorphic rocks under the microscope: classification, textures, microstructures and mineral preferred-orientations. • Vernon, R. H. & Clarke, G. L. (2008): Principles of Metamorphic Petrology.

Pyroxene is a mafic mineral, and often forms green to black crystals (see Digital Kit examples). Gabbro contains olivine crystals (greenish-grey), feldspar (grey to white), and pyroxene (black). See if you can identify any pyroxene crystals in the gabbro or peridotite (the labels available in the Digital Kit can help you identify pyroxene ...

Evidence for slow cooling can be seen in the crossed polars picture, in which Plagioclase grains (white grains with dark striping due to Crystal Twinning) are partly to completely enclosed by Pyroxene grains (all the colored grains: yellow, orange, red, and blue).

Olivine pyroxene amphibolite This coarse-grained rock from Scourie in Scotland is one of a series of metamorphosed intrusive rocks that have been extensively studied since they played an important role in helping geologists to separate two deformation phases in the ancient rocks of northern Scotland.

The differences between the A and B sites are important and are key to understanding the mechanical properties of pyroxene. The pyroxene structure is not uniformly strong and the regions between the chains are relatively weak such that they are likely to break - or cleave - …

Garnet clinopyroxene plagioclase granulite. This garnet-clinopyroxene-plagioclase granulite comes from near Slishwood in the northeastern end of the Ox Mountains inlier, a belt of extremely high-grade metasediments and metabasites whose age is uncertain. The rocks survive widespread Grampian epidote amphibolite facies retrograde alteration.