Superheated ice: true compression fractures and fast internal melting.
Internal melt figures can be nucleated in ice without the presence of a vapor bubble. Their form and growth are fracture-like, different from the normal Tyndall stars, which do contain vapor bubbles. Normal Tyndall figures that grow rapidly are not oriented in the basal plane, and very rapid internal melting gives a peculiar, systematic growth of clouds of Tyndall figures.
Knight
C A
CA
Knight
N C
NC