schist
Concise Oxford English Dictionary © 2008 Oxford University Press:
schist /ʃɪst/
▶noun Geology a coarse-grained metamorphic rock which consists of layers of different minerals and can be split into thin irregular plates.
– origin C18: from Fr. schiste, via L. from Gk skhistos ‘split’, from the base of skhizein ‘cleave’.
'schist' also found in these Oxford entries:

