Physico-chemical study of an exogenic fulgurite from a thunderstorm on 10th August 2013 in Dallas, TX

Droplet-like exogenic fulgurites comprise a minor grouplet of natural glasses resulting from powerful lightning strikes. Reports on such type-V fulgurites are scarce in the literature. In this work, a fulgurite specimen from the thunderstorm that took place on 10th August 2013, in Dallas, TX, USA, has been analyzed using X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and infrared and Raman spectroscopy techniques. X-ray diffraction revealed the amorphous nature of the exofulgurite, and X-ray fluorescence showed a high Si, Al and Ca content. Infrared and Raman spectroscopy were key in revealing clear Si–O modes related signatures and a very significant presence of water (OH/H2O). A parallel with glassy silicate materials, but also with opal-A, was essential in the understanding of the fulgurite’s characteristics. In particular, Raman data evidenced the exofulgurite to have a high degree of depolymerization.