Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. It is composed primarily of the mineral calcitee (CaCO3) and usually contains other minerals such as: clay minerals, micas, quartz, pyrite, iron oxides and graphite.
Under the conditions of metamorphism the calcite in the limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals.
ost marble forms at convergent plate boundaries where large areas of Earth's crust are exposed to regional metamorphism. Some marble also forms by contact metamorphism when a hot magma body heats adjacent limestone or dolostone
Marble is usually a light-colored rock. When it is formed from a limestone with very few impurities it will be white in color. Marble that contains impurities such as clay minerals, iron oxides or bituminous material can be bluish, gray, pink, yellow or black in color.
Marble can be cut & polished and used as floor tiles, architectural panels, facing stone, window sills, stair treads, columns and many other pieces of decorative stone.