The layer of soil with the largest rock particles is the R horizon, also known as bedrock.

Here's why:

* R horizon: This is the unweathered parent material, essentially solid rock. It's the foundation upon which all other soil layers form.

* Other layers: As you move upwards in the soil profile, the rock particles become smaller and more weathered due to processes like erosion and decomposition.

Important Note: While the R horizon is technically a soil layer, it's not considered true soil because it lacks the organic matter and structure that define soil.