A calculus (plural calculi), often called a stone, is a concretion of material, usually mineral salts, that forms in an organ or duct of the body. Formation of calculi is known as lithiasis (/ˌlɪˈθaɪəsɨs/). Stones can cause a number of medical conditions.Some common principles (below) apply to stones at any location, but for specifics see the particular stone type in question.Calculi are not to...More