Fig. 6

Sulphurous lump with embedded Sclerolinum tubes collected from Kemp Caldera. a Sulphurous lump with embedded Sclerolinum tubes collected from Kemp Caldera, scale bar is 30 mm. b Detail of the tubes embedded in the sulphurous lump pictured in (a), scale bar is 1 mm. c SEM image of the surface of subsample of the sulphurous lump, scale bar is 50 μm. The bright crystals in this image showed a large sulphur peak when examined using energy dispersive x-ray spectroscopy (EDS). d EDS elemental map of sulphur lump subsample, yellow colours highlight the distribution of sulphur, blue of silicon. Red arrows show Sclerolinum tubes in section, scale bar is 2 mm. e Detail of Sclerolinum tube section that is embedded within the sulphurous lump, scale bar is 200 μm