Serpentine is a group of hydrous minerals that is commonly formed along faults and other interfaces in Earth where water is able to react with other anhydrous minerals. Because serpentine has a number of unusual physical properties, it is hypothesized that serpentine-group minerals play an essential role in the dynamics of boundaries between tectonic plates. Furthermore, serpentine may control where earthquakes can or cannot occur.  However, serpentine is only stable through a narrow range of pressure and temperature conditions, which has hindered experimental efforts to unravel its behavior. The objective of this project is to clarify further the rheology and associated deformation microstructures of antigorite, the high pressure and temperature phase of serpentine, using a variety of experimental techniques.