Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated, although there are exceptions. In geology, the term marble refers to metamorphosed limestone, but its use in stonemasonry more broadly encompasses unmetamorphosed limestone.
Marble forms when a pre-existing limestone rock is heated to such extreme temperatures that the minerals grow larger and fuse together. The dark, foliated bands cutting through the marble are a different kind of metamorphic rock, such as slate.