Fine-grained rock is a type of sedimentary rock composed of small particles. It includes shale, SLATE, and chert, which are all five-letter words. Shale is a type of mudstone that is formed from clay minerals and silt-sized particles. SLATE is a metamorphic rock that is formed from the alteration of shale due to heat and pressure. Chert is a sedimentary rock composed of silica and is usually found in limestone.