Three-Dimensional X-ray Reflections from Anthracite and Meta-Anthracite
Sabri Ergun 1,
Morris Mentser 1, and
H. J. O'Donnell 1
1 Special Coal Research Section, U.S. Bureau of Mines, Pittsburgh, Pennsylvania
Careful analysis of x-ray scattering intensities of demineralized metaanthracites and high-rank anthracites formed during the Pennsylvanian geological period has revealed the presence of three-dimensional (hkl) reflections of graphite, demonstrating unequivocally that coals graphitize with metamorphism. Graphitization has been observed also with a coal formed before the Cambrian period, much earlier than most coals. A significant degree of graphitization occurs by coalification when the graphite-like layers attain a size of 25 to 30 angstroms as compared to 100 A or more by the heat treatment of amorphous carbons.