According to the U.S. General Services Administration, limestone is important because it is widely used in architectural applications for walls, decorative trim and veneer. It is less commonly used in making sculptures because of its porosity and softness.
Limestone is a sedimentary rock that is primarily composed of calcium carbonate, also known as calcite, or the double carbonate of calcium and magnesium, also known as dolomite. It is common for limestone to contain tiny fossils, shell fragments and other fossilized debris. Some varieties of limestone contain extremely fine grain. Limestone is typically gray, but it can also be white, yellow or brown. During major geological events, limestone deposits sometimes undergo metamorphism and recrystallize as marble.