Which rock type is formed from particles such as sand, shells, pebbles, and other fragments cemented together?

• A. Sedimentary rock
• B. Metamorphic rock
• C. Igneous rock
• D. Crystal rock

Answer: (A)

Rocks are classified by how they form. Particles like sand, shells, and pebbles are sediments that are deposited and then become glued together as minerals precipitate from water, a process called cementation (often accompanied by compaction). When these grains are cemented and lithified, they form sedimentary rock. Examples include sandstone from sand, limestone from shells, and conglomerate from pebbles. Metamorphic rocks come from existing rocks transformed by heat and pressure, igneous rocks form from cooling magma or lava, and “crystal rock” isn’t a standard category here. So the described rock type is sedimentary.