A variety of gemstones have been found in skarn. Garnet, ruby, and sapphire are the gems most commonly found in skarn. Here are a few examples: Demantoid garnet and topazolite have been mined from the Antetezambato skarns near Ambanja, northern Madagascar. Sapphires are mined from skarn in the Andranondambo Region of Madagascar. Yellow scapolite has been mined from a skarn…

Skarns often contain a diverse assemblage of metamorphic minerals. The mineral assemblage in a skarn is determined by the lithology of the invaded rock, the chemistry of the invading liquid, and the temperature of the rock environment. Metamorphic minerals that characterize the skarn environment include a wide range of calc-silicates, many types of garnet, and a…

In the example described above, skarn formed in a carbonate rock unit adjacent to a magma intrusion. There are numerous other geological situations where skarn can be formed. These include: Skarn can form with various water inputs. These include include:

Skarns can form on both sides of the boundary between a magma body and its surrounding rock mass. Those formed on the igneous side of the contact are known as endoskarns. Those formed on the country-rock side of the contact are known as exoskarns. Exoskarns form when the original chemistry of a rock mass is altered –…

Most skarns form when carbonate rocks such as limestone, dolostone, or marble are intruded by a magma body and altered by contact metamorphism and metasomatism. At the time of intrusion, the heat of contact metamorphism is the primary agent of change. Then, as the magma cools, it releases hot, acidic, silicate-rich fluids. Some magmas contain up to several percent…

Skarn is a metamorphic rock that has been chemically and mineralogically altered by metasomatism. Metasomatism is the alteration of rocks by hot, chemically-active fluids that flow or diffuse through the rocks and cause recrystallization and compositional change. Skarn commonly forms around the edges of a magma body that intrudes a nearby rock mass. Rocks formed or altered by the interaction…