Non-destructive, high-resolution X-ray micro-CT of a Hairy Stalagmite: investigating the structural details of a biogenic speleothem

Three-dimensional X-ray micro-computed tomography permits to investigate the internal structure of objects at a high resolution without altering its original form. It also facilitates the rendering and visualization of a virtual replica, which can be subjected to rigorous and complex analyses. In the present study, micro-computed tomography was used to investigate a unique and fragile speleothem (cave formation) named a “Hairy Stalagmite”. Non-destructive analyses have revealed the calcareous internal structure of this speleothem, which consists of hollow, interconnected tubes. Rendered two-dimensional cross-sections also clearly revealed the outline of a once dense root nest that formed part of the speleothem’s biogenic origin. The internal structure was further visualized using an image sequence of two-dimensional cross-sections to create a video that “brings the speleothem to life”, also illustrating its complexity and variability. Statistical analyses revealed structural variability in void fraction, which is likely related to changing environmental conditions. In addition, the micro-computed tomography data were used as input for additive manufacturing (three-dimensional printing) in order to produce an enlarged replica of the Hairy Stalagmite sample, which made physical inspection possible. This combined approach represents the first of its kind and provides much benefit for future studies.