Imaggeo on Mondays: Electron cloud gone wrong

Imaggeo on Mondays: Electron cloud gone wrong

Deciphering the past history of rocks and what they might reveal about the Earth’s future is a key part of geology, and tools such as Ion Probes can be used by Earth Scientists to extract valuable information about a rock’s past.

Today’s Imaggeo on Monday’s image was acquired by Sarah Glynn, a researcher at the University of the Witwatersrand, in South Africa, who was analysing a potential calcite reference material (a mineral homogeneous enough to be considered a benchmark for future analyses on others minerals of the same composition) using Secondary Ion Mass Spectrometry. By assessing its suitability as a reference material for oxygen isotope measurements in calcite (a carbonate mineral), one can more accurately determine the past temperature conditions in which certain rocks formed by looking at the differences in the relative abundances of the isotopes of oxygen (16O & 18O).

When doing analyses with an Ion Probe, it is important to coat the sample (in this case a round epoxy disc, in which some calcite fragments are embedded) with a thin layer of gold to make the surface conductive. As an additional measure to compensate for charge building up, a flood of electrons is directed to the surface of the sample.Occasionally however, if the sample is not sufficiently coated, or the coating itself is damaged – perhaps scratched – a kind of ‘lightning strike’ can occur, which can be quite damaging to both the sample and instrument alike, but can also be strangely beautiful when they create striking fractal patterns, such as was the case in this photograph.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at

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Laura Roberts Artal is the Outreach and Dissemination Manager at The Water Innovation Hub (University of Sheffield). Laura also volunteers as the Associate Director of Communications for Geology for Global Development. She has also held a role in industry as Marketing Manager for PDS Ava (part of PDS Group). Laura was the Communications Officer at the European Geosciences Union from the summer of 2014 to the end of 2017. Laura is a geologist by training and holds a PhD in palaeomagnetism from the University of Liverpool. She tweets at @LauRob85.

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