The occurrence of iron silicides in a fulgurite: Implications for fulgurite genesis

Authors

Christopher J. Stefano, Michigan Technological UniversityFollow
Stephan A. Hackney, Michigan Technological UniversityFollow
Anthony R. Kampf, Natural History Museum of Los Angeles

Document Type

Article

Publication Date

1-16-2020

Department

A. E. Seaman Mineral Museum; Department of Materials Science and Engineering

Abstract

Rapidly formed eutectic textures are observed in Fe silicides in a fulgurite from Michigan. The 14 cm-diameter fulgurite was formed in sandy glacial till in 2014 near Houghton Lake, Michigan. Spherical droplets of iron silicides up to ∼200 μm in diameter were found in the natural glass. Back-scattered electron images of some droplets show a eutectic intergrowth texture of two iron silicides with individual crystals up to ∼1 μm in maximum dimension. X-ray diffraction study showed the specimens to be an intergrowth of naquite (FeSi) and linzhiite (FeSi₂) or naquite and xifengite (Fe₅Si₃). Droplets also contain minor native silicon, Fe-Ti silicides, and/or other Ti- rich phases which were discovered during TEM observations. It is important to note that the lower-temperature phase luobusaite (Fe₃Si₇) was not observed in any droplets, indicating rapid quenching of the fulgurite, consistent with a natural origin during a lightning strike as opposed to an artificial origin, e.g., resulting from a downed power line.

Publication Title

The Canadian Mineralogist

Recommended Citation

Stefano, C. J., Hackney, S. A., & Kampf, A. R. (2020). The occurrence of iron silicides in a fulgurite: Implications for fulgurite genesis. The Canadian Mineralogist, 58(1), 115-123. http://doi.org/10.3749/canmin.1900019
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/1694