Answer :
Final answer:
Limestone is mainly made of calcium carbonate, which forms from the accumulation of organic materials like marine organism shells. For a rock to be classified as limestone, it should contain at least 50% calcium carbonate. The reaction of limestone with hydrochloric acid confirms its composition due to the fizzing caused by the release of carbon dioxide gas.
Explanation:
Limestone Composition
Limestone is predominantly composed of the mineral calcium carbonate (CaCO3). This rock primarily forms from the accumulation of organic materials such as the shells and skeletons of marine organisms, including mollusks and crustaceans. These remains, along with the remains of plankton, contribute to the limestone in varying degrees, especially in tropical marine environments.
To qualify as limestone, a rock must contain at least 50% calcium carbonate. When limestone undergoes chemical processes, such as the reaction with hydrochloric acid, it demonstrates its composition by effervescing or fizzing, which is a clear indicator of the presence of CaCO3. Some limestone varieties may also contain dolomite (CaMgCO3), which is another type of carbonate mineral found in limestone formations.
