What is a Protolithic rock?

A protolith (from Ancient Greek πρωτο (prōto) ‘first’, and λίθος (líthos) ‘stone’) is the original, unmetamorphosed rock from which a given metamorphic rock is formed. For example, the protolith of a slate is a shale or mudstone. Identifying a protolith is a major aim of metamorphic geology.

How is graphite schist formed?

Graphite schist is uncommon, but can form from metamorphosis of sedimentary beds containing abundant organic carbon. This may be of algal origin. Metamorphosis of felsic volcanic rock, such as tuff, can produce quartz-muscovite schist.

What minerals are in graphite schist?

Graphite and pyrite often occur together. When they are together in a rock, they suggest that the rock was originally sediment that contained lots of organic matter. Here is a sample of a schist that is composed of graphite (black) with layers of pyrite (greenish yellow) crystals.

What is a Phenocrysts in geology?

« Back to Glossary Index. A large crystal within an igneous rock. These can be seen within phaneritic and porphyritic rocks.

What is schist made of?

Most schists are composed largely of platy minerals such as muscovite, chlorite, talc, sericite, biotite, and graphite; feldspar and quartz are much less abundant in schist than in gneiss.

What is talc schist?

A regional metamorphic rock composed predominantly of talc, and displaying a schistosity. The rock forms by the metamorphism and deformation of ultrabasic igneous rocks in regional terranes. From: talc schist in A Dictionary of Earth Sciences »

What is schist rock used for?

Schist is formed from shale or mud but at a much higher temperature than slate. Schist is not a very strong rock, so it is not often used as a building material. However it can be used for garden decoration, paving and sometimes sculpture.

What is graphite mineral?

graphite, also called plumbago or black lead, mineral consisting of carbon. Graphite has a layered structure that consists of rings of six carbon atoms arranged in widely spaced horizontal sheets.

What type of mineral is graphite?

crystalline carbon
Graphite is a naturally occurring form of crystalline carbon. It is a native element mineral found in metamorphic and igneous rocks. Graphite is a mineral of extremes. It is extremely soft, cleaves with very light pressure, and has a very low specific gravity.