Here's why:

* Limestone and dolostone: These are sedimentary rocks primarily composed of calcium carbonate (limestone) or calcium magnesium carbonate (dolostone).

* Metamorphism: When these rocks are subjected to intense heat and pressure deep within the Earth's crust, they undergo a process called metamorphism. This transforms their texture and mineral composition.

* Marble formation: During metamorphism, the original limestone or dolostone recrystallizes, forming a denser, more crystalline rock – marble. The heat and pressure cause the calcite crystals in the limestone or dolostone to grow larger and interlock, giving marble its characteristic veining and patterns.

So, while marble is a metamorphic rock, its origin lies in the sedimentary rocks limestone and dolostone.