Marble reacts with acid. Marble a metamorphic rock that contains calcium carbonate (CaCO3) and other carbonate minerals. Here a piece of marble is dropped into a beaker with 0.2 M hydrochloric acid (HCl). Carbon dioxide (CO2) bubbles are produced: CaCO3 + HCl -> CaCl2 + H2O + CO2 (similar reactions for other cabonates). This is the mechanism by which acid rain erodes marble statues and structures.