Large Crystals Of Granite Surrounded By Mica Schist

It is often referred to as schistosity because of its large mica flakes.

Large crystals of granite surrounded by mica schist.

Hi kevin my understanding is schist is a coarse grained metamorphic rock that consists of layers of different minerals mica among them along with chlorite talc hornblende and graphite and can be split into thin irregular plates. The mountains are primarily composed of granite surrounded by an envelope of mica schist and much older rocks such as quartzite. Schist is a metamorphic rock made mostly of mica mineral formed under the heat and compression of tectonic forces. The black gray and white grains are mostly silt or smaller size grains of quartz and feldspar.

A porphyroblast is a large mineral crystal in a metamorphic rock which has grown within the finer grained matrix porphyroblasts are commonly euhedral crystals but can also be partly to completely irregular in shape. Schist and slate are very similar in that they are made from the same rock types except it is subjected to more heat and pressure. Where as mica is it s own mineral and forms in flaky layers. This is a microscopic view of a garnet grain that has grown in schist.

Large crystals cause schist rocks to reflect lots of light which gives it a very shiny appearance. The large black grain is the garnet the red elongate grains are mica flakes. The most common porphyroblasts in metapelites metamorphosed mudstones and siltstones are garnets and staurolites which stand out in well foliated metapelites such as schists. Mica crystal healing properties information.

Garnet mica schist in thin section.