Fig. 2: Back-scattered electron (BSE) images showing the distribution of nanolites in scoriae of the FL eruption.

Nanolites occur (a, c) at the boundaries between two different melts as spherical-subspherical crystals. The white arrows indicate the more evolved silicate melt composition. At higher magnification, (b, d) the crystal-poor glass shows a mottled texture (highlighted by the orange arrows), which may indicate the presence of nanolites, but of a size which is below the resolution of the technique. Nanolites are also observed along the (e, f) boundaries of concave structures, which may represent shells consisting of oxide crystals that nucleate on the surface of bubbles, where the bubble is then lost by detachment and not preserved49. The sequence of concave structures may represent several generations of oxide nucleation on bubbles, forming multiple shells.