Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble may be foliated. Geologists use the term "marble" to refer to metamorphosed limestone; however, stonemasons use the term more broadly to encompass unmetamorphosed limestone. Marble is commonly used for sculpture and as a building material.
Most 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 a material used in prestige architecture and interior design. It is used for its beauty in architecture and sculpture. It is used for its chemical properties in pharmaceuticals and agriculture. It is used for its optical properties in cosmetics, paint, and paper. It is used because it is an abundant, low-cost commodity in crushed stone prepared for construction projects. Marble has many unique properties that make it a valuable rock in many different industries.
Marble occurs in a very wide range of colors. Marble formed from the purest limestones is white in color. Iron oxide impurities in the limestone will produce a yellow, orange, pink or red color. Clay minerals can produce gray colors that often occur in bands after the compositional stratification of the original limestone. Abundant bituminous materials can produce dark gray to black marble. Marble that contains serpentine often has a green color.