Fissility (geology)

In geology, fissility is the ability or tendency of a rock to split along flat planes of weakness (“parting surfaces”).

[2] Fissility is differentiated from scaly fabric in hand sample by the parting surfaces’ continuously parallel orientations to each other and to stratification.

Fissility is distinguished from scaly fabric in thin section by the well-developed orientation of platy minerals such as mica.

Planes of weakness are developed in sedimentary rocks such as shale or mudstone by clay particles aligning during compaction.

[3] Planes of weakness are developed in metamorphic rocks by the recrystallization and growth of micaceous minerals.