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Marble
Marble is a metamorphic rock that forms when limestone is subjected to the heat and
pressure of metamorphism. Under the conditions of metamorphism the calcite in the
limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals. A related
rock, dolomitic marble, is produced when dolostone is subjected to heat and pressure.
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.
In the construction trade, the term "marble" is used for any massive, crystalline calcitic rock
(and some non-calcitic rocks) useful as building stone. For example, Tennessee Marble is
really a massive, highly fossiliferous gray to pink to maroon Ordovician dolostone, known as
the Holston Formation by geologists.
Its extremely varied and colorful patterns make it a favorite decorative material, and are
often imitated.
Marble occurs in large deposits that can be hundreds of feet thick and geographically
extensive
Marble is crushed and used as an aggregate in highways, railroad beds, building foundations
and other types of construction. It is also cut into pieces of specific size to produce dimension
stone. These are used in monuments, buildings, sculptures, paving and other projects.
Marble has always been highly valued for its beauty, strength, and resistance to fire and
erosion.
Marble does not split easily into sheets of equal size and must be mined with care. The rock
may shatter if explosives are used. Marble is a metamorphic rock that forms
when limestone is subjected to the heat and pressure of metamorphism. Under the
conditions of metamorphism the calcite in the limestone recrystallizes to form a rock that is a
mass of interlocking calcite crystals. A related rock, dolomitic marble, is produced
when dolostone is subjected to heat and pressure.
It is a very attractive stone. It is economical because it is relatively easy to cut and engrave. In
comparison to rocks like granite, it is not as resistant to acid precipitation and tends to lose
edges and detail over time.
After being sanded with progressively finer abrasives, marble can be polished to a high luster.
This allows attractive pieces of marble to be cut, polished and used as floor tiles, architectural
panels, facing stone, window sills, stair treads, columns and many other pieces of decorative
stone.