Coal

Rock group Metamorphic
Metamorphism type Regional
Protolith It goes like this:

Peat

Lignite

Bituminous coal

Anthracite

Coal in hand sample

Bituminous coal
Allegheny Formation bituminous coal
Coal and pyrite intermingled
Anthracite
Anthracite displaying greasy lustre

Coal in thin section

Stay tuned for explorable images!

Bituminous coal, plane polars

Bituminous coal, plane polars

Magnification: 40x Click here for crossed polars: https://youtu.be/t8hNoiBO0ag

Bituminous coal, crossed polars

Bituminous coal, crossed polars

Magnification: 40x Click here for plane polars: https://youtu.be/FNPce8bR95s