Unusual Devonian coal: A new type of jet

A new type of jet from continental Devonian sediments is described. The substrate for gagatization was fragments of Archaeopteris plants, whose burials in sandstone strata are characterized by a kind of spheroidal weathering of organic matter; the material is completely fusainized. This type of jet combines the properties of classical jet and inertinite. The new type of jet was named tsilmanite—after the place of its discovery.