a high pressure, low temperature metamorphic rock characteristic of subduction zones.
A low temperature, high pressure regionally metamorphic rock, containing abundant glaucophane. .... More
metamorphic rock formed under conditions of high pressure (in excess of 5000 bars) and relatively low temperature, often containing the blue minerals glaucophane (an amphibole) and kyanite.
Metamorphic rock formed under great pressures, but not so great temperatures.
Blueschist (IPA: ) is a rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures, approximately corresponding to a depth of 15 to 30 kilometers and 200 to ~500 degrees Celsius. The blue color of the rock comes from the presence of the mineral glaucophane.