Marble

Marble is a term strictly applied to any limestone susceptible of polish, though often inaccurately extended to alabaster, serpentinite or granite. Marbles are generally partly or completely crystalline ill texture, the latter - such as the white marble of Carrara - being known as saccharoid. The beauty of many varieties depends upon the presence of fossils in them, as in the madrepore marbles with fossil corals in the Devonian rocks, the encrinital and bird's-eye marbles of the Carboniferous rocks of Bristol aiid Derbyshire and the fresh-water Paludina marbles of Purbeck and Sussex made up of the snail-shells now known as Vivipartts. The more completely crystalline marbles owe their texture to metamorphic action, known technically as marmarosis. This may be due to the heat from contact with igneous rocks or pressure. The white statuary marble of Carrara, in Tuscany, used by Michelangelo and Canova, and imported as "Sicilian" marble, is that employed by modern sculptors. Its age is variously stated as Carboniferous, Triassic and Liassic. From the same source comes the grev-veined marble, known in Italy as bardiglio. "Somewhat similar are the marbles of Mount Pentelicus, in Attica, used by Phidias and Praxiteles in the Parthenon, as seen in the Elgin marbles in the British Museum: and of the island of Paros, represented by the Venus de' Medici. Black marble is obtained from Carboniferous rocks at Ashford, Derbyshire, and various places in Ireland.

It contains bituminous matter and is, therefore, known mineralogically as anthraconite. True red marble is uncommon, some of the rocks so called being porphyritic felsites. Green marbles such as verd antique, Irish green marble from Connemara, and Mona marble from Anglesey, are ophicalcites, or mixtures of serpentine and limestone of metamorphic origin. Landscape or Cotham marble, from the White Lias of the Rhartic series near Bristol, is a dull grey clayey limestone, with tree-like markings produced by infiltrated oxide of manganese. Algerian and Mexican onyx or onyx-marble is a translucent brownish and yellowish stalagmite (q.v.) formed by the evaporation of carbonated water, the alabaster of the ancients being a similar stone.