Coined in Sweden as a term for deposits of iron that were found in rocks near a pluton, today skarn is more broadly understood to refer to any metamorphic zone that develops around contact areas nearby igneous rock intrusions. These zones are characterized by the introduction of large amounts of iron, silicon, aluminum, and magnesium into limestones and other carbonate sedimentary rocks. In addition to tactite, skarns are known by a number of other names, such as igneous-metamorphic and pyrometasomatic deposits.