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 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.Due to the amount of transformation and formation of crystals, various stones with different textures and shapes are formed in terms of small and large. Marble stones that have large crystals and are light gray to cream white are called crystal stones, and the white type is known among Chinese stone marketers. Marble stones have higher density and erosion resistance than travertine stones and are used to pave pavements for high-traffic areas of floors and stairs.
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. 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. 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.
Marble stones can also be classified in terms of metamorphism and the amount of crystals or calcite crystals in it and in terms of color spectrum.
Types of marble based on the amount of transformation are:
Porcelain stone: A type of marble that has an all-crystalline texture with fine and fine-grained grains. This type occurs in areas where the intensity of change is less.
Crystal stone: This type of stone has all crystalline texture with coarse grains and the same size. Crystal sync occurs in logic where the intensity of change is medium to high.
The types of marble in terms of color are: