The surface of a vitrain fragment isolated from low-carbon coal viewed under a microscope (x2000 magnification)
Vitrain is a lithotype of coal formed from the bark of large plants. Known for its glossy appearance, vitrain typically occurs in thin bands, between 3 and 10 millimeters in width. It has a brittle texture and typically forms cubical pieces when broken. Chemically, vitrain stands out among coal lithotypes by hosting large concentrations of germanium. Combustion of vitrain proves a vital source of germanium production, where the element can be extracted from the leftover ash.
↑Ward, Colin R. (2003). "Coal Geology". Encyclopedia of Physical Science and Technology. pp.45–77. doi:10.1016/B0-12-227410-5/00111-3. ISBN978-0-12-227410-7. Vitrain takes the form of thin, homogeneous bands of black, glassy material, usually ranging from 3 to ∼10 mm in thickness. It is generally very brittle and characterized by a close-spaced fracture pattern cutting across the layers.