DEFINITION: Limestone is a type of sedimentary rock that is primarily composed of calcium carbonate, which is derived from the remains of marine organisms such as coral and shells. It is formed over millions of years by the accumulation of sediment at the bottom of oceans, lakes, and other bodies of water. Limestone is a soft, porous, and easily carved material, making it a popular choice for building and sculpting. It is available in a range of colors, from light beige to dark gray, and can have a variety of textures, from smooth to rough. Due to its porosity, limestone requires regular cleaning and maintenance to prevent staining and deterioration over time