The mineral found in both limestone and marble is calcite.

* Limestone is primarily composed of calcite, a calcium carbonate mineral (CaCO3).

* Marble is formed when limestone is subjected to heat and pressure, causing the calcite crystals to recrystallize and form a denser, more compact rock.

While other minerals can be present in both limestone and marble in smaller amounts, calcite is the defining mineral component that distinguishes them.