Skarn

Skarn is rock resulting from contact metamorphism of intrusions of various types of grained rock (gabbro granite); the initial rock is a carbonate rock transformed by metasomatose (q.v.) with the introduction of a number of elements (Si, Al, Fe) which combine with those of the initial rock to give a wide variety of silicates. Skarn masses often have single mineral zones (e.g. grenatites) and can enclose workable concentrations of various metals (Fe, Cu, Mo, W, etc.), called pyrometasomatic (q.v.) deposits.