The terminology of a slate
Slate is a compact and fine-grained metamorphic rock. Due to its excellent fracture cleavage it can be split into thin plates and slabs. The original material for slate is commonly shale.
A rock which can be used for roofs and façades and which comprises mainly phyllosilicates (micas) and shows a penetrative fracture cleavage.
A ribbon is a structure on the cleavage surface of a slate, consisting of multicoloured stripes which can be straight, wavy or crumpled and generally traces the bedding.