Marble, which is a type of metamorphic rock, forms from either limestone or dolostone. The formation of marble occurs due to these minerals being under extreme pressure and temperatures. Although the main mineral in marble is calcite, its composition also includes a combination of other minerals, such as quartz, mica and graphite.
Marble can be white in appearance if it does not have impurities, but is also found in other colors when it does contain impurities. On the Mohs hardness scale, marble has a hardness value of three, which makes it useful for carving.
Marble is a building material used since ancient times. It is also a popular material utilized as highway aggregate in crushed form. Because marble is made up principally of calcite, which is calcium carbonate, it is susceptible to environmental conditions such as acid rain that can degrade this material.