What is the term for the portion of soil derived from rock?

The correct term for the portion of soil that is derived from rock is mineral matter. Mineral matter consists of the inorganic components of soil, which result from the weathering of parent rock material. These minerals not only provide essential nutrients to plants but also influence the soil's texture, structure, and water-holding capacity.

In contrast, organic matter refers to the decomposed materials from living organisms, which contribute to soil fertility and microbial activity but do not come from rock. Topsoil is the uppermost layer of soil, rich in organic material and nutrients, but it includes both organic and mineral components. Subsoil is located beneath topsoil and contains minerals but is typically lower in organic matter content. Therefore, mineral matter accurately describes the part of soil that originates from the weathering of rock material.