schist

Any of various medium-grained to coarse-grained metamorphic rocks composed of laminated, often flaky parallel layers of chiefly micaceous minerals.

A rock the constituent minerals of which have assumed a position in more or less closely parallel layers or folia, due not to deposition as a sediment, but—in large part, at least—to metamorphic action, which has caused a rearrangement or imperfect crystallization of the component minerals, or the formation of new ones, these. in the course of the process, having assumed the parallel arrangement characteristic of the rock.

Any crystalline rock having a foliated structure (see foliation) and hence admitting of ready division into slabs or slates. The common kinds are mica schist, and hornblendic schist, consisting chiefly of quartz with mica or hornblende and often feldspar.

Any crystalline rock having a foliated structure and hence admitting of ready division into slabs or slates.

any metamorphic rock that can be split into thin layers