Slate is a fined grained metamorphic rock. Shale is the parent rock. It is made up of clay minerals. Shale can metamorphose into slate, phyllite, schist or gneiss depending on the degree of heat and pressure it is exposed to. Slate is the least metamorphosed of this group. Meaning that it has been subjected to the least amount of heat and pressure (low-grade metamorphism). It is associated with regional metamorphism do to mountain building.
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Slate is foliated and easily splits into thin, flat, parallel planes. This along with its chemical inertness and thermal stability make slate useful for many purposes. It is used for roofing shingles, floor tiles, pool tables and laboratory benches.