Marble is categorized as a metamorphic rock. Some of the minerals it contains is calcite and/or dolomite.

Metamorphic rock is actually limestone that for some time has been exposed to high temperature and pressure. Such circumstances caused these rocks to go through a process of change known as metamorphoses, the reason they are called metamorphic rocks.

Due to changes in the environment, minerals found in these rocks go through a molten phase, which causes the appearance of swirls or bands that we see in marbles.