The Dean (Fire Clay) coal in Knox County, Kentucky, does not contain the megascopically-visible ash-fall ton stein present in most other sections of the coal bed. Like the Fire Clay tonstein, a low-ash portion of the coal is enriched in rare earth elements ( > 2400 ppm, on ash basis). In addition to kaolinite produced in the diagenesis of volcanic glass, transmission electron microscopy studies indicate the coal contains primary kaolinite, La-Ce-Nd-Th monazite, barium niobate, native gold, and Fe-Ni-Cr spinels. The mineral assemblages, particularly the kaolinite-monazite association and its similarity to the tonsteins in coal to the east, demonstrate the coal was subject to the REE-enriched volcanic ash fall, apparently just at a more dilute level than at locations where the tonstein is present.