Boulders, when broken down by weathering and erosion, become a variety of smaller materials, depending on the specific weathering processes involved:

Physical Weathering:

* Smaller rocks: The boulder is broken into smaller pieces, ranging from pebbles to cobbles.

* Sand: Further breakdown of the smaller rocks can create sand grains.

* Dust: Fine particles of rock can become dust, which can be carried by wind.

Chemical Weathering:

* Clay: Chemical reactions can transform minerals in the boulder into clay minerals.

* Dissolved minerals: Some minerals in the boulder can dissolve into the surrounding water.

Biological Weathering:

* Soil: Plant roots, burrowing animals, and other biological activity can break down rocks and contribute to soil formation.

Overall:

The breakdown products of a boulder can range from large rocks to microscopic particles, and will vary depending on the types of weathering involved. The end result is a gradual decrease in the size of the rock fragments, contributing to the formation of soil, sand, and other geological materials.