Submicron-scale mineralogy of lithotypes and the implications for trace element associations: Blue Gem coal, Knox County, Kentucky

James C. Hower, Debora Berti, Michael F. Hochella, Susan M. Rimmer, Darrell N. Taulbee

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Transmission electron microscopy accompanied by energy-dispersive spectroscopy and selected area electron diffraction of density-gradient separates from two lithotypes of the low-ash, low-sulfur Blue Gem coal, eastern Kentucky, revealed an array of previously unrecognized (in this coal, and arguable in most others) sub-micron minerals, some <10 nm in size. The sample representing the 1.22–1.24 specific gravity fraction of the middle bench contains a mineral identified as a La-, Ce-, Nd-bearing monazite; other minerals with Cr–Fe, Cu–Fe–S, Fe–Zn-S, and Pb; and areas, probably comprising agglomerates of several grains, if not several minerals, with concentrations of Mg, Ca, Ti, Fe, Zn, Zr, and Mo. The sample representing the 1.30–1.31 specific gravity fraction of the basal lithotype has aggregates of particles enriched in Mg, Ca, Ti, and Fe. Individual grains not specifically quantified include Cr–Ni–Mn–Cu–Fe–S, Ag–S, and Cu–S. Detailed investigation of one area (most of the variation within a <4 μm2 region) demonstrates the presence of greenockite (CdS); minute phases containing Ni–Co–Ge and Ag–Cd–Bi, the latter with a more evident S association than the former; metallic Bi; nisnite (Ni3Sn); silver cadmium; manganosite (MnO); and siderite. Some minerals, such as the monazite, are most likely of detrital or tuffaceous origin. Many of the other assemblages could be of hydrothermal origin, a hypothesis supported by known regional geochemical and coal rank trends, but not previously demonstrated in mineral assemblages at the 10's of nm scale in this region.

Original languageEnglish
Pages (from-to)73-82
Number of pages10
JournalInternational Journal of Coal Geology
StatePublished - May 2018

Bibliographical note

Funding Information:
This work used shared facilities at the Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure (NanoEarth) , a member of the National Nanotechnology Coordinated Infrastructure (NNCI), supported by NSF ( ECCS 1542100 ).

Funding Information:
This work was supported by National Science Foundation grant CBET-1510861 to the University of Kentucky.

Publisher Copyright:
© 2018 Elsevier B.V.


  • Cadmium
  • Low-ash coal
  • Rare earth elements
  • Silver
  • Transmission electron microscopy

ASJC Scopus subject areas

  • Fuel Technology
  • Geology
  • Economic Geology
  • Stratigraphy


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