what is marble a rock how are there so many colors?
Marble is a metamorphic rock. That is a pre-existing original rock bearing calcium carbonate (CaCO3) has been transformed into a marble through pressure and temperature variation acting on that original rock deep in the Earth (15km). Marbles are primarily made up of Calcite crystals (A version of CaCO3). But if these crystals carry impurities such as other elements (ex: Mg in the place of Ca) the rock will have different colors.
Marble is metamorphosed limestone or dolomite. Therefore it is composed mainly of calcium and/or magnesium carbonate. Limestone and dolomite are rarely compositionally homogeneous. Their chemical composition will vary through the rock, and the inclusion of small amounts of silt and fossil remains will influence the composition of the rock. Metamorphism will recrystallise the minerals in the rock. The addition of fluids from a nearby intrusion will potentially add some minerals which will also influence the composition of the rock. These inhomogeneities in composition from original and introduced minerals will result in a marble showing bands of different colours. It is also possible that deep weathering and groundwater movement through the marble as it nears the ground surface will create colour banding due to the movement of minerals in and out of the marble.
