A thinly layered rock composed of clay-sized particles is called shale.

Here's why:

* Clay-sized particles: Shale is formed from the accumulation of very fine sediment, specifically clay.

* Thinly layered: Shale exhibits a distinct layering, often referred to as "fissility," which allows it to break easily along these layers.

* Rock: Shale is a sedimentary rock, meaning it is formed from the accumulation and cementation of sediments.

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