Marble is a metamorphic rock made out of limestone. When limestone is subjected to tremendous pressure for a long time (like if limestone is buried under a lot of other rock or an ocean) it gets squashed into marble. Marble is more beautiful than limestone and tougher, and so people like to use it for buildings.
But marble is also rarer than limestone is, and more expensive. A lot of marble is white, but marble can come in all different colors. In ancient Greece and Rome, people used marble (especially white marble) to make statues, and they used colored marble in patterns to make hard floors that would last a long time.
Carving a marble statue
Sometimes people also used marble in thin sheets on the walls of fancy buildings like churches or palaces, to make a brick wall look fancier. When marble was too expensive, people used travertine, or limestone, or they used plaster frescoes on their walls that were painted to look like marble.
For example, the Parthenon in Athens is built entirely of marble – that was very expensive. But Notre Dame cathedral in Paris is built of limestone (partly because there isn’t as much marble near Paris). The Colosseum in Rome is built of brick and travertine, with marble only for the sculpture and the seats. Domitian’s palace in Rome is brick, but with thin sheets of marble covering the brick walls. And many houses in Pompeii have only plaster walls painted to look like marble.
DK Eyewitness Guides: Building, by Philip Wilkinson (2000).
Geology: A Golden Guide from St. Martin’s Press, by Frank Rhodes (2001).
Ancient marble quarrying and trade (1986). A collection of papers by specialists, for specialists, about marble in ancient Greece and Rome.