Rocks found in a river bed are typically rounded and smooth. This is due to the constant abrasion and erosion caused by the flowing water and the rocks bumping against each other.

Here's a breakdown of the types of rocks you might find:

* Sedimentary rocks: These are the most common rocks found in riverbeds. They form from the accumulation and cementation of sediments like sand, gravel, and mud. Examples include:

* Conglomerate: Made of rounded pebbles and gravel cemented together.

* Sandstone: Formed from sand grains.

* Shale: Formed from compacted clay.

* Igneous rocks: While less common, igneous rocks can also be found in riverbeds, especially if the river originates in a volcanic region. These rocks form from cooled magma or lava. Examples include:

* Basalt: A dark, fine-grained volcanic rock.

* Granite: A light-colored, coarse-grained igneous rock.

* Metamorphic rocks: These rocks form when existing rocks (igneous, sedimentary, or other metamorphic rocks) are transformed by heat and pressure. Examples include:

* Marble: Formed from metamorphosed limestone.

* Slate: Formed from metamorphosed shale.

The specific type of rocks you find will depend on the geological history of the river and the surrounding area.