Here's why:

* Limestone is primarily composed of calcium carbonate (CaCO3).

* Dolomite is a carbonate mineral composed of calcium magnesium carbonate (CaMg(CO3)2).

* Marble is a metamorphic rock formed from limestone or dolomite. It's essentially recrystallized calcium carbonate or calcium magnesium carbonate.

The defining characteristic of the carbonate mineral group is the presence of the carbonate anion (CO3)2-.