Limestone is sedimentary rock formed from the decayed shells of living organisms. It may be white, light tan, or light gray in color and is used in the construction of both every day and more formal structures.
Ex: Many famous landmarks in the United Kingdom, such as St Paul's Cathedral and Cleopatra's Needle, are made with limestone gathered from both domestic and foreign quarries.
Ex: For the construction of the Houses of Parliament, limestone quarried from outside the City of London was selected as a building material.
The Egyptian pyramids were capped with a limestone casing that allowed them to appear shiny. This is due to the variety of animal shells contained in the stone.
Ex: At the top of the pyramids of Giza, some of the limestone covering can still be seen glinting in the bright desert sun.
Ex: Much of the limestone that archaeologists believe originally covered the Egyptian pyramids has worn off over time.
Marble is stone, usually limestone or other sedimentary rock, that has changed after being subjected to heat or pressure. It is usually highly polished and used in construction.
Ex: The beautiful, but cold marble staircase that led from the mansion's entrance to the private residence above intimated the young girl who had come to visit her rich aunt and uncle.
Ex: For a sculpture as magnificent as the one you are describing, you should use white marble. You want the detail to be the focus, not the color of the piece.
A marble can also refer to the game marbles, which is a game made of round pieces of highly polished glass. Those these marbles are not actually made from marble; they are referred to that way because they often have similar coloration patterns that can mimic the patterns found in true marble.
Ex: In the 1960s, marbles became a very popular game amongst young people. You would often see children spending their recess playing against each other.
Ex: If you play marbles "for keeps", it means that the other players have a chance of keeping the marbles you brought into the game with you.