Trace Minerals in West Virginia Coals:

Sphalerite is a somewhat common trace mineral in West Virginia coals filling voids originally present in the peat.  In the case shown here, the minerals sphalerite, pyrite and kaolinite grew within open cavities in semifusinite ("fossil charcoal") in the Pittsburgh coal.  In semifusinite, the original plant cell walls were carbonized by fire into strong, pure carbon, remnants of the original cell walls with openings where the cell contents were located.  Dissolved ions in the peat waters precipitated into various minerals in these voids as the peat formed.  Silicon and aluminum were most abundant and crystallized into very common kaolinite, Al₄(Si₄O₁₀)(OH)₈, iron and sulfur formed less common pyrite, FeS₂, zinc and sulfur formed sphalerite, ZnS, and barium and sulfur formed barite, BaSO₄.  The sphalerite shown in this SEM image also contained a significant amount of barium in an unknown association with the sphalerite.  Sphalerite in coal also commonly contains small amounts of cadmium and is probably the major site of Cd in coals.  Other associations of sphalerite with galena and clausthalite in semifusinite have been noted in West Virginia coals.
 

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Page last revised: March 1, 2002

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