What are rocks or mineral fragments with a diameter of 2mm or more referred to as?

Rocks or mineral fragments with a diameter of 2mm or more are referred to as rock fragments. This term is used in geology and soil science to describe the coarse materials that can vary in composition, originating from the weathering of larger rock formations. Understanding the size classification of soil particles is crucial for various applications, including agriculture, construction, and environmental science, as these fragments can significantly influence the physical properties of the soil, such as drainage, aeration, and nutrient availability.

The other terms listed do not accurately describe fragments of this size. For instance, sandy soil typically consists of finer particles and would not include well-defined rocks or mineral fragments of larger diameter. Platy structure refers to a type of soil structure characterized by flat, plate-like aggregates rather than individual rock pieces. PED, which stands for "ped," is a term used to describe soil aggregates but does not specifically denote larger fragments of rock. Therefore, rock fragment is the precise term that suits the definition provided in the question.