Final answer:
Travertine is primarily composed of calcite, making it a variety of limestone. It is well-known for its use in famous structures such as the Colosseum in Rome.
Step-by-step explanation:
Travertine is primarily composed of the mineral calcite, which is also the primary component of limestone. This makes limestone the correct answer to your question. Travertine, a form of limestone, has been widely used in construction due to its durability and aesthetic appeal. For example, the Colosseum in Rome is known for its golden appearance, which comes from the use of travertine. Not to be confused with sandstone, which is a clastic sedimentary rock composed of sand-sized minerals and rock fragments, limestone is predominantly composed of skeletal pieces of marine organisms such as corals and foraminifera and thus includes a variety of types such as chalk, coquina, micrite, travertine, oolite, tufa, and fossiliferous limestone.