Marble an abundant type of stone that has many uses and applications in building, decoration and art. It is prized for its beauty and shine. In fact, the word “marble” comes from the Greek “marmaros”, meaning “shining stone”. It has been highly prized as a material for sculpture through the centuries. But because marble is a metamorphic rock, it started out as something quite different.
• Formation and Composition
Marble is a non-foliated, metamorphic rock composed mainly of calcite or dolomite crystals. These crystals are the result of metamorphosed limestone being melted by heat and pressure and solidifying again with the crystals tightly interwoven and becoming larger crystals. A marble that is composed of calcite limestone is called a calcite marble, while marble that is metamorphosed from dolomitic limestone is called a dolomitic or magnesian marble. Outside of geology, the term marble is often loosely applied to any limestone that can be polished or is suitable for building. However, geologically, only metamorphosed limestone is true marble.
• Color of Marble
Marble comes in many colors. It may be a soft, pure white or it can range from light gray to black. Marble that is white comes from metamorphosed limestone that is very pure or dolomit protolith. Colored varieties of marble abound and may be green, pink, beige, yellow or red. The colors are caused by impurities, that is, other minerals in the limestone. These minerals might include clay, silt, sand, or iron oxides. In the case of veined or patterned marble, these impurities get rearranged and recrystallized during metamorphism, causing the color to group in bands that run through the marble.
Marble is mined by the quarry method, in which large slabs are cut out of marble formations. Carrara in Tuscany, Italy, is famous for being the site where all of the marble used for the Pantheon and Trajan’s Column in Rome was quarried. Michelangelo’s “David” is carved from Carrara marble. Marble is mined in many other countries around the globe as well, including Spain, Italy, Pakistan, Canada, India and the United States. Within the US, Vermont is considered to produce the finest marble but it is mined in several other states such as Massachusetts, New Hampshire, Tennesee, Alabama and Colorado. The town of Marble, Colorado boasts the largest slab of marble ever quarried.
Marble is porous, although the pores in the surface are very tiny and impossible to see. However, they do allow for the absorption of moisture and other liquids which can corrode or stain the marble. Water, oils and acid rain can affect the appearance of marble and its durability. Impurities in the marble itself can also decrease durability of the stone.
Today, marble is a popular building material used in many architectural projects and to create decorative effects. Because it can be obtained in many sizes and shapes, marble tiles for walls and floors are popular in interior design. Marble has been used throughout history in creating some of the world’s most beautiful structures. The ancient Greeks used marble to construct the Parthenon. The Taj Mahal is completely covered in white marble. White marble was a favorite medium for sculptors because of its beauty, its soft appearance and its ability to allow light to penetrate the stone to a small degree before reflecting it back. To quote Michelangelo: “I saw the angel in the marble, and carved until I set him free.”