Marble is a metamorphic rock formed from the metamorphism of limestone or dolostone, which are sedimentary rocks primarily composed of calcite or dolomite minerals. The metamorphism process occurs when the limestone or dolostone is subjected to high temperature, pressure, or both, deep within the Earth's crust.
During the metamorphic process, the original minerals in the parent rock recrystallize, resulting in changes to the rock's texture, composition, and crystal structure. The heat and pressure cause the calcite or dolomite minerals to recrystallize into larger, interlocking crystals, creating the characteristic veining and swirls in marble. This process also gives marble its uniform, crystalline appearance and its unique colors, which are often influenced by the presence of other minerals and impurities in the parent rock.