Calcite can form rocks of considerable mass and constitutes a significant part of all three major rock classification types. It forms oolitic, fossiliferous and massive limestones in sedimentary environments and even serves as the cements for many sandstones and shales.
Limestone becomes marble from the heat and pressure of metamorphic events.
Calcite is even a major component in the igneous rock called carbonatite and forms the major portion of many hydrothermal veins. This is even the primary ingredient in many antacid tablets. The 50mm Orange Calcite Sphere is two inches in diameter.