The mineral particles found in the layers of a soil, including topsoil and subsoil, were originally weathered from parent rock.

Here's a breakdown:

* Parent rock: This is the bedrock or underlying geological formation that the soil developed from. It can be igneous, sedimentary, or metamorphic rock.

* Weathering: The process of breaking down parent rock into smaller particles through physical (like freezing/thawing) and chemical (like acid rain) processes.

* Soil formation: Over time, these weathered particles, along with organic matter, water, and air, mix and form the different layers of soil (horizons).

So, the mineral particles in soil are essentially fragments of the parent rock that have been broken down and transformed by weathering processes.