Answer:
Limestone
Explanation:
Marble is a metamorphic rock which is formed, when the sedimentary rock named limestone is subjected to extreme pressure and temperature condition. During this process of metamorphism, the calcite minerals present in the rock limestone undergoes the process of re-crystallization, thereby producing a much more denser and higher grade rock where the calcite crystals alters into more forcibly equigranular crystals.
This is how limestone after going through the process of metamorphism, changes into a metamorphic rock named marble.
