Which type of sedimentary rock is characterized by visible fragments or clasts such as sandstone and shale?

• A. Organic
• B. Chemical
• C. Metamorphic
• D. Clastic

Answer: (D)

Think about how sedimentary rocks form. When rocks break down into pieces and those pieces are transported, deposited, and then compacted and cemented, they become clastic (detrital) sedimentary rocks. The clue here is “visible fragments or clasts.” Sandstone and shale are classic examples, since sandstone is made up of sand-sized grains and shale consists of smaller fragments of clay and silt that originate from weathered rocks. This distinguishes them from chemical rocks, which form by minerals precipitating from solution and usually lack visible clasts, and from organic/biochemical rocks, which come from accumulated plant or animal remains, or from metamorphic rocks, which are transformed by heat and pressure rather than formed from loose fragments. So the described rock type is clastic.