A substance X is used as a building material and insoluble in water

A substance X is used as a building material and insoluble in water. When reacts with dil. HCl, it produces a gas which turns lime water milky. Predict the substance and write the chemical equation involved.

The substance X is CaCO3, used as a building material and insoluble in water. The reaction involve with dil. HCl is: