Chalcopyrite, like pyrite, formed within the peat early in the coal's
history. Chalcopyrite crystals could form anywhere within the peat,
but often preferentially grew within open voids such as in semifusinite
("fossil charcoal") along
with other sulfide minerals. 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. In this SEM
photomicrograph of the Stockton coal from Boone County WV, kaolinite, chalcopyrite,
and sphalerite fill cavities in semifusinite.
Chalcopyrite and galena both grew within a single 30 µm opening (dots
at the bottom of the photograph are each 10 µm apart). Silicon
and aluminum were most abundant and crystallized into very common kaolinite,
Al4(Si4O10)(OH)8, iron, sulfur
and copper formed less common chalcopyrite, zinc and sulfur formed sphalerite,
ZnS, and lead and sulfur formed galena, PbS. In this study, copper statistically
correlated only with lead, suggesting that this relationship between chalcopyrite
and galena may be somewhat widespread in West Virginia coals. Chalcopyrite
was observed in moderate amounts in 18 of 24 coal samples examined with
the SEM in an unpublished study by the WVGES.
|To request specific information from a Survey geologist click here.|
Page last revised: March 1, 2002
Please send questions, comments, and/or suggestions to webmaster.
Page created and maintained by: West Virginia Geological & Economic Survey Address: Mont Chateau Research Center Cheat Lake exit off I-68 P.O. Box 879 Morgantown, WV 26507-0879 Telephone: 1-800-WV-GEOLOgy (1-800-984-3656) or 304-594-2331 FAX: 304-594-2575 Hours: 8:00 a.m. - 5:00 p.m. EST, Monday - FridayPermission to reproduce this material is granted if acknowledgment is given to the West Virginia Geological and Economic Survey.