What is the primary characteristic of a boulder?

The primary characteristic of a boulder is that it is defined as a large rock. Geologically, boulders are typically considered to be rocks that are larger than a foot in diameter, and they are often formed from the weathering and erosion of other rock formations. This definition sets boulders apart from smaller stones or gravel, which do not meet the size criteria to be classified as boulders. Additionally, while minerals are the building blocks of rocks, they are not categorized under the broader term of boulders, and a sandy beach refers to a geographical feature rather than a rock classification. Therefore, identifying a boulder primarily emphasizes its size and solid rock composition.