deeLiving Inc- Ocean / Reef Rock is Limestone carbonate sedimentary rock that is often composed of the skeletal fragments of marine organisms such as coral, foraminifera, and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO₃). Collected at Stone Quarry in Indonesia, no damage comes to the Nature Coral Reefs. Suits for Bed rocks or as Decorations for Aquarium also acting as a pH buffering agent.