Formed when limestone is subjected to high pressures over time, Marble plays an important role in many aspects of our everyday lives, perhaps without us even realizing it. Categorized as a metamorphic rock, Marble is a composition of recrystallized carbonate minerals. The stone has a hardness level of 3-4 Mohs, a density of 2.55-2.7 kilograms per cubic centimeter, and a compressive strength of 70-140 Newtons per square millimeter. It is most common to find light shades of Marble, although some darker shaded forms of Marble do exist. The most sought after, and therefore expensive, Marble tends to be completely white, or otherwise very light, in shade.
Marble deposits can be found in various countries around the globe. Such European countries as Italy, Ireland, Spain, Greece, Russia, Romania, Sweden, and Germany, in addition to others in Asia, are among the globe's leading producers of this valuable rock. The United States of America is also a high level Marble producer, with states such as Alabama and Texas having especially large deposits to be found within their borders. It is, however, Italy, China, India, and Spain who dominate global Marble production.
Marble is a metamorphic rock, therefore meaning that it forms where convergent plate boundaries are exposed to regional metamorphism. During metamorphism, a certain calcite from limestone deposits will recrystalize as the texture of the rock changes. The crystals begin very small, with only a sugar-like speck able to be seen at first. Thereafter, the metaphoric process continues to grow the crystals, until larger, interlocking calcite crystals can be clearly seen. This process will obscure any previous fossil or sedimentary structures the limestone previously had. Once the process is complete, a shiny, crystalline rock will appear, with the Marble clearly distinguishing itself from common limestone.
The majority of Marble deposits will be turned into small crushed stones, or “dimension” stones. Crushed stone Marble will be used as an aggregate on highways, railroad beds, building foundations, and in other types of construction. That marble processed as “dimension” stones calls for pieces of marble to be cut in certain pieces and dimensions. These stones will be used in monuments, buildings, sculptures, and other artistic projects. When a very light shade of white Marble is found, it is commonly used as a whitening agent. Paints, whitewash, putty, plastics, grout, cosmetics, and paper all have very small amounts of powdered Marble as a whitening agent as well.
Marble is mined, or rather “quarried”, worldwide. Quarrying Marble begins by taking a sample from the Marble deposit, in order to test it’s purity. Once tested and approved, the Marble slabs are then drilled out with diamond-tipped drills. Italy, Portugual, China, India, and Spain combine to make up 57% of the world’s total Marble production. The United States is also a leading producer, selling 72,300 tons in 2005. In the year 2006, 11.8 million tons of crushed Marble was produced, equating to a value of $116 million USD.