Serpentinite is a type of metamorphic rock that primarily consists of the mineral serpentine. It forms when ultramafic rocks, like peridotite, undergo alteration due to heat and pressure, often in the presence of water. This process can occur in tectonically active regions, such as subduction zones, where oceanic crust is pushed beneath continental crust. The rock is typically greenish in color and has a smooth, often shiny surface. Serpentinite is significant in geology because it can indicate the presence of asbestos, a group of minerals that can be harmful to health. Additionally, it plays a role in the carbon cycle by sequestering carbon dioxide.