Which of the following is NOT a classification of soil texture?

Soil texture is determined by the size of soil particles and is typically classified into several categories based on the predominant particle size. The main classifications include sand, silt, and clay, which denote three distinct components of soil. Each of these components plays a critical role in influencing the soil's characteristics, such as drainage and nutrient retention.

Rock, however, is not classified as a soil texture. Instead, rock material is generally considered part of the geological context or parent material from which soil is derived. It consists of larger particles and aggregates that do not fit into the finer classification of soil textures. By understanding these classifications, horticulturists can better assess soil suitability for different types of plants and agricultural practices.