A coarse-grained metamorphic rock which consists of layers of different minerals and can be split into thin irregular plates
= alum shale.
A metamorphic rock containing quartz and mica which resembles slate in being easily split
A schist of a greenish colour; specifically (usually in form greenschist) a schistose or foliose rock with a greenish colour resulting from an abundance of chlorite, epidote, and albite, and formed by metamorphism of basic igneous rocks.
A metamorphic rock with a blue colour, formed under conditions of high pressure and low temperature