CoachA foliation is a planar fabric that pervades a rock: a set of closely spaced parallel surfaces, made by aligned platy or flattened grains or by thin layers, along which the rock splits most easily. Schistosity is the foliation of a schist, made by aligned grains coarser than about . A cleavage is a foliation of a fine-grained rock made by its deformation; slaty cleavage is the cleavage of a slate, made by sheet silicates too small to be seen with the naked eye, and so closely set that the rock can be split almost anywhere into thin sheets. An axial-planar cleavage is a cleavage parallel, or nearly parallel, to the axial planes of the folds in the same rocks.
