Antigorite (IMA symbol: Atg[1]) is a lamellated, monoclinic mineral in the phylosilicate serpentine subgroup with the ideal chemical formula of (Mg,Fe2+)3Si2O5(OH)4.[2] It is the high-pressure polymorph of serpentine and is commonly found in metamorphosed serpentinites. Antigorite, and its serpentine polymorphs, play an important role in subduction zone dynamics due to their relative weakness and high weight percent of water (up to 13 weight % H2O).[3][4] It is named after its type locality, the Geisspfad serpentinite, Valle Antigorio in the border region of Italy/Switzerland[5] and is commonly used as a gemstone in jewelry and carvings.