n. 片岩

[ noun ]
any metamorphic rock that can be split into thin layers
<noun.substance>

Schist \Schist\ (sh[i^]st), n. [Gr. ? divided, divisible, fr. ?
to divide: cf. F. schiste. See {Schism}.] (Geol.)
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.