All You Need to Know About Marble
What is Marble?
Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. It is composed primarily of the mineral calcite (CaCO3) and usually contains other minerals, such as clay minerals, micas, quartz, pyrite, iron oxides, and graphite.
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.
How Does Marble Form?
The transformation of limestone into marble usually occurs at convergent plate boundaries where large areas of Earth’s crust are exposed to the heat and pressure of regional metamorphism. Some marble also forms by contact metamorphism when a hot magma body heats adjacent limestone or dolostone. This process also occurs at convergent plate boundaries.
Before metamorphism, the calcite in the limestone is often in the form of lithified fossil material and biological debris. During metamorphism, this calcite recrystallizes and the texture of the rock changes.
In the early stages of the limestone-to-marble transformation, the calcite crystals in the rock are very small. In a freshly-broken hand specimen, they might only be recognized as a sugary sparkle of light reflecting from their tiny cleavage faces when the rock is played in the light.
As metamorphism progresses, the crystals grow larger and become easily recognizable as interlocking crystals of calcite. Recrystallization obscures the original fossils and sedimentary structures of the limestone. It also occurs without forming foliation, which normally is found in rocks that are altered by the directed pressure of a convergent plate boundary.
Recrystallization is what marks the separation between limestone and marble. Marble that has been exposed to low levels of metamorphism will have very small calcite crystals. The crystals usually grow in size and as the level of metamorphism progresses.
Clay minerals within the marble will alter to micas and more complex silicate structures as the level of metamorphism increases. Some might contribute to the formation of gem minerals such as corundum – the mineral of ruby and sapphire.
Physical Properties and Uses of Marble
Marble occurs in large deposits that can be hundreds of feet thick and geographically extensive. This allows it to be economically mined on a large scale, with some mines and quarries producing millions of tons per year.
Most marble is made into either crushed stone or dimension stone. Crushed stone is used as an aggregate in highways, railroad beds, building foundations, and other types of construction.
Dimension stone is produced by sawing marble into pieces of specific dimensions. These are used in monuments, buildings, sculptures, paving and other projects. We have an article about “the uses of marble” that includes photos and descriptions of marble in many types of uses.
- Color: Marble is usually a light-colored rock. When it is formed from a limestone with very few impurities, it will be white in color. Marble that contains impurities such as clay minerals, iron oxides, or bituminous material can be bluish, gray, pink, yellow, or black in color. Marble of extremely high purity with a bright white color is very useful. It is often mined, crushed to a powder, and then processed to remove as many impurities as possible. The resulting product is called “whiting.” This powder is used as a coloring agent and filler in paint, whitewash, putty, plastic, grout, cosmetics, paper, and other manufactured products.
- Acid Reaction: Being composed of calcium carbonate, marble will react in contact with many acids, neutralizing the acid. It is one of the most effective acid neutralization materials. Marble is often crushed and used for acid neutralization in streams, lakes, and soils.
It is used for acid neutralization in the chemical industry as well. Pharmaceutical antacid medicines such as “Tums” contain calcium carbonate, which is sometimes made from powdered marble. These medicines are helpful to people who suffer from acid reflux or acid indigestion. Powdered marble is used as an inert filler in other pills. - Hardness: Being composed of calcite, marble has a hardness of three on the Mohs hardness scale. As a result, marble is easy to carve, and that makes it useful for producing sculptures and ornamental objects. The translucence of marble makes it especially attractive for many types of sculptures. The low hardness and solubility of marble allows it to be used as a calcium additive in animal feeds. Calcium additives are especially important for dairy cows and egg-producing chickens. It is also used as a low-hardness abrasive for scrubbing bathroom and kitchen fixtures.
- Ability to Accept a Polish: 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.
Another Definition of Marble
The name “marble” is used in a different way in the dimension stone trade. Any crystalline carbonate rock that has an ability to accept a polish is called “marble.” The name is sometimes used for other soft rocks such as travertine, verd antique, serpentine, and some limestones.
Marble is a rock widely used in buildings, monuments, and sculptures. It consists chiefly of calcite or dolomite, or a combination of these carbonate minerals. Marble is a type of metamorphic rock formed from limestone. Marble is found in many countries, including Belgium, France, Great Britain, Greece, India, Italy, and Spain.
Marble is formed from limestone by heat and pressure in the earth’s crust. These forces cause the limestone to change in texture and makeup. This process is called recrystallization. Fossilized materials in the limestone, along with its original carbonate minerals, recrystallise and form large, coarse grains of calcite. Impurities present in the limestone during recrystallization affect the mineral composition of the marble that forms. The minerals that result from impurities give marble wide variety of colors. The purest calcite marble is white. Marble containing hematite has a reddish color. Marble that has limonite is yellow, and marble with serpentine is green.
Marble does not split easily into sheets of equal size and must be mined carefully. The rock may shatter if explosives are used. Blocks of marble are mined with channeling machines, which cut grooves and holes in the rock,
Uses. Marble has long been highly valued for its beauty, strength, and resistance to fire and erosion. The ancient Greeks used marble in many buildings and statues. The Italian artist Michelangelo used marble from Carrara, Italy, in a number of sculptures.
Extremely pure calcite marble is used for most statues. Large blocks of colored marble are, used for columns, floors, and other parts of buildings. Smaller pieces of such marble are crushed or finely ground and used as abrasives in soaps and other products. Crushed or ground marble is also used in paving roads and in manufacturing roofing materials and soil treatment products.
Marble 1:
Marble is limestone that has crystallized naturally over a period of time. Marble is classified into four groups, Groups A, B, C, and D. These are broad classifications and relate only to soundness and working qualities. However, for the purpose of this maintenance guide marble has been classified as exterior or interior maintenance of marble. The test used for water absorption is ASTM C97. Marble is cut into blocks, slabs or tile in various thickness and sizes. Marble flooring is very sensitive to acids and alkalis and can be stained if spills are not wiped up immediately. If marble flooring is installed in an area where staining liquids are liable to cause problems, then the flooring should be sealed and finish applied.
Marble 2:
Marbles are basically metamorphosed limestones. Once limestone is subjected to heat and pressure, the calcium carbonate re crystallizes into marble.
Marbles have similar characteristics to limestones and are typically used on the same applications, though, marbles are almost always more aesthetically valuable and available in much wider range of colors.
There are several types of marbles, including calcites (from calciferous limestones), dolomites (from dolomitic limestone), serpentines (typically green marbles) and travertines (sedimentary limestone). Each of these is similar in their composition, that being predominantly calcium carbonate, and their capability to take a polish. The stone that is quarried west of Belen in central New Mexico is a travertine marble.
Many years ago, there was a cataclysmic shift in the earth’s crust and the Rio Grande Valley appeared. The Sandia mountains were pushed up on the east side bringing granite to the surface and leaving limestone on the top or backside of the mountain. This limestone was once the floor of a vast ocean that covered the entire southwest U.S. If you drive along south 14 you can see the layers of limestone along the roadside. This same limestone is used to make cement at the plant in Tijeras, New Mexico. When the valley was formed, there were openings made in the earth’s crust which allowed volcanoes to form and many hot springs to appear. These hot springs were present west of Belen, and as they came to the surface, the water passed through the limestone beds.
The calcium carbonate in the limestone went into suspension in the water and once it got to the surface the water evaporated and it became travertine.
One characteristic of all Travertines is the presence of small voids that were caused by air bubbles in the hot water. At times when the springs went cold, onyx was formed. It is not uncommon to find bands of onyx among travertine beds.
Marbles are suitable for both interior and exterior applications but it should be noted that with today’s environment containing so many pollutants, if a polish finish is specified on marble, it will not last.