Antigorite

This specimen is antigorite, a green, fibrous to bladed mineral belonging to the serpentine group. Antigorite commonly forms in metamorphosed ultramafic rocks, produced when mantle-derived rocks react with water under heat and pressure. The specimen shows the characteristic elongated, layered, and slightly splintery texture typical of antigorite, with a dull to silky sheen and olive-green coloration. Unlike chrysotile (the fibrous asbestos variety of serpentine), antigorite forms platy or bladed crystals and is considered the high-temperature, high-pressure serpentine polymorph. Antigorite is an important mineral in geology because it plays a major role in subduction zones, where it helps transport water deep into the Earth’s mantle, influencing volcanism and plate tectonics.