Calcarea carbonica is a homeopathic medicine used to treat a range of ailments including anxiety, depression, headaches, skin conditions, and digestive problems. Some synonyms for calcarea carbonica include calcium carbonate, oyster shell, and Calc-C. Calcium carbonate is a mineral substance that is found naturally in rocks, marine organisms, and eggshells. Oyster shell, as the name suggests, comes from the shells of oysters and is often used as a dietary supplement for calcium. Calc-C is an abbreviated name for calcarea carbonica and is commonly used in homeopathic circles. Whatever name it goes by, calcarea carbonica has been used for many years as a natural remedy for a variety of health issues.