Marble is a metamorphic rock.
Metamorphic rocks are created through a process known as metamorphism. These rocks, as their name suggests, are the products of rocks that have "morphed" from their previous form, or parent rock, into a new form through this slow-moving and natural process. There are several different types of metamorphic rock.
Metamorphism
Metamorphism is a process in which the rocks deep below the earth's surface change into a different type of rock due to intense heat and pressure. Rocks that are located anywhere from 12 to 16 kilometers below the earth's surface begin to morph when the temperature rises above 212 degrees Fahrenheit due to the presence of magma. Because the rocks are so deep below the surface, immense pressure, also known as lithostatic pressure, aids the heat in changing them. Rocks eventually adjust to these conditions and become metamorphic rock.
Types of Metamorphic Rock
Metamorphic rock exists in two basic forms: foliated and non-foliated. Foliated metamorphic rocks are recognized by their multilayered appearance. These metamorphic rocks look as though they are made of many thin layers of minerals, giving them a banded look. Foliated metamorphic rocks are generally formed at a lower temperature and pressure than non-foliated metamorphic rocks. Non-foliated metamorphic rocks are formed deeper below the earth's surface where the temperature is higher and the pressure is greater. These metamorphic rocks do not have minerals that give them a layered or banded appearance.
The Rock Cycle
Metamorphic rocks are part of the rock cycle which consists of three main types of rock: igneous, sedimentary and metamorphic. The rock cycle is used in geology to describe how all types of rocks are related, and how, under the right conditions, each type can transform into the other types. Both igneous and metamorphic rocks can become sedimentary through weathering and erosion. Both igneous and sedimentary rocks can become metamorphic rock under intense heat, pressure and with the addition of magma. Sedimentary rock becomes igneous rock once again after cycling through metamorphism to become metamorphic rock and then through a melting and cooling process caused by magma. This is a consistent cycle that doesn't change.
Common Metamorphic Rocks
Metamorphic rocks are commonly used for both building and decorative purposes. Examples of foliated metamorphic rocks are slate, gneiss and schist. These are widely used as building stones in architectural structures. Examples of non-foliated metamorphic rocks are marble and quartzite. These rocks are also used for ornamental purposes as well as in all forms of construction.
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