Which clastic rock typically contains angular clasts?

• A. Breccia
• B. Sandstone
• C. Shale
• D. Conglomerate

Answer: (A)

In clastic sedimentary rocks, the shape of the fragments shows how far they were transported: angular clasts indicate little transport and minimal abrasion, while rounded clasts result from longer transport that wears the edges smooth. Breccia is the rock that preserves those sharp, jagged fragments, usually large and angular, held together by a cementing matrix. This angularity points to rapid deposition from nearby sources, such as landslides or debris flows, where the fragments aren’t worn down before burial.

In contrast, conglomerate contains rounded clasts because the particles have been tumbled and eroded during transport in a stream or river. Sandstone is built from sand-sized grains, which aren’t defined by angular clast shape, and shale consists of fine clay-sized particles with a layered, mudstone texture rather than discrete angular fragments.

So the rock that typically contains angular clasts is breccia.