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Published June 1965 | public
Journal Article

Zoned magnetite and platy magnetite in Cornwall type ore deposits

Abstract

Eighteen selected specimens from the Cornwall type ore deposits of Pennsylvania were studied by optical examination of polished sections and by means of an electron microprobe X-ray analyzer (without calibration). The elements Ti, Si, V, Mn, Co, and Ni occur in the magnetite crystals in very low concentrations with little variation. In zoned magnetite crystals, yellowish color bands parallel to crystal faces are marked by increased concentrations of Al and Mg. Some magnetite crystals contain minute oriented inclusions whose concentration decreases outwards; the Mg concentration decreases outwards as well, correlating with the variation in concentration of the inclusions. Platy magnetite crystals, pseudomorphs after hematite, contain cores of lighter colored magnetite; the outer magnetite contains slightly less Fe and slightly more impurities in solid solution than the inner magnetite core that replaces hematite.

Additional Information

© 1965 Society of Economic Geologists. Sept. 12, 1964. Contribution No. 64-14 from the College of Mineral Industries. We wish to thank Drs. A. A. Socolow and D. M. Lapham of the Pennsylvania Geologic Survey for their interest and advice during this project, and for reading critically a first draft of the manuscript; Dr. Lapham guided and facilitated visits to Cornwall where samples were collected, and other field localities, and provided additional samples of Cornwall ore. Dr. J. D. Ridge kindly provided ore samples from Cornwall, French Creek, Warwick, and Grace mines. The work was supported by grant MCS-5800 from the Mineral Conservation Section, College of Mineral Industries, The Pennsylvania State University.

Additional details

Created:
August 22, 2023
Modified:
October 17, 2023