Kalamata olives are known as a black olive, although they are actually dark purple in color. Native to Greece, Kalamata olives can be eaten plain or chopped up to be used in a dish. Made from fully ripe olives, Kalamata olives are marinated in olive oil or vinegar and are widely available in grocery stores. While Kalamata olives are high in sodium, they are also rich in healthy fats and contain a natural antioxidant.