What Are Small Pieces of Rock Called?

Regardless of their size, all pieces of rock that break off of other rocks are called sediment. Wind, water and gravity are the primary causes of rocks breaking off into smaller pieces and being moved around. Sediment can travel short or long distances depending on what led to the initial movement, and this movement can cause even further erosion to the rock. When the sediment is no longer transported, it collects with other sediment to form piles of rocks or sand.