vitrain
{{Short description|Lithotype of coal}}
File:Поверхня_сколу_вітрену.jpg
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.{{Cite web |title=Vitrain {{!}} Railway, Transportation, Logistics {{!}} Britannica |url=https://www.britannica.com/science/vitrain |access-date=2023-08-12 |website=www.britannica.com |language=en}}{{Cite web |title=Vitrain - an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/chemistry/vitrain#:~:text=Vitrain%20takes%20the%20form%20of,pattern%20cutting%20across%20the%20layers |access-date=2023-08-12 |website=www.sciencedirect.com}} It has a brittle texture and typically forms cubical pieces when broken.{{Cite web |date=19 June 2023 |title=Vitrain: Mineral information, data and localities |url=https://www.mindat.org/min-9460.html |access-date=11 August 2023 |website=MinDat}} Chemically, vitrain stands out among coal lithotypes by hosting large concentrations of germanium.{{Cite journal |last=Stadnichenko |first=Taisia |date=1953 |title=Concentration of Germanium in the Ash of American Coals: A Progress Report |url=https://pubs.usgs.gov/circ/1953/0272/report.pdf |journal=Geological Survey Circular |issue=272 |via=USGS.gov}} Combustion of vitrain proves a vital source of germanium production, where the element can be extracted from the leftover ash.