for: Marble (disambiguation)

Marble is a nonfoliated metamorphic rock resulting from the metamorphism of limestone, composed mostly of calcite (a crystalline form of calcium carbonate, CaCO₃). It is extensively used for sculpture, as a building material, and in many other applications. The word "marble" is colloquially used to refer to many other stones that are capable of taking a high polish.

Etymology

The word "marble" derives from the Ancient Greek μάρμαρον (marmaron) and that from μάρμαρος (marmaros), "crystalline rock", "shining stone", perhaps from the verb μαρμαίρω (marmairō), "to flash, sparkle, gleam". This stem is also the basis for the English word marmoreal, meaning "marble-like".

Origins

Marble is a metamorphic rock resulting from regional or rarely contact metamorphism of sedimentary carbonate rocks, either limestone or dolomite rock, or metamorphism of older marble. This metamorphic process causes a complete recrystallization of the original rock into an interlocking mosaic of calcite, aragonite and/or dolomite crystals. The temperatures and pressures necessary to form marble usually destroy any fossils and sedimentary textures present in the original rock.

Pure white marble is the result of metamorphism of very pure limestones. The characteristic swirls and veins of many colored marble varieties are usually due to various mineral impurities such as clay, silt, sand, iron oxides, or chert which were originally present as grains or layers in the limestone. Green coloration is often due to serpentine resulting from originally high magnesium limestone or dolostone with silica impurities. These various impurities have been mobilized and recrystallized by the intense pressure and heat of the metamorphism.

Types

Some historically important kinds of marble, named after the locations of their quarries, include

White marbles, like Carrara in Italy, Royal White and Beijing White in China and Malagori of Pakistan, have been prized for sculpture since classical times. This preference has to do with the softness and relative isotropy and homogeneity, and a relative resistance to shattering. Also, the low index of refraction of calcite allows light to penetrate several millimeters into the stone before being scattered out, resulting in the characteristic "waxy" look which gives "life" to marble sculptures of the human body.