mineralsantigorite

Antigorite is a mineral species in the serpentine group with the chemical formula Mg3Si2O5(OH)4. It is a hydrous magnesium phyllosilicate and one of the serpentine minerals that form by hydration of ultramafic rocks. Antigorite is commonly found in serpentinites and ophiolites and is notable for its relative stability at higher temperatures and pressures within the serpentine family, particularly in subduction-zone environments.

Occurrence and formation

Antigorite forms by metasomatic hydration (serpentinization) of ultramafic rocks such as peridotite and dunite, typically in low-temperature, high-fluid conditions. In tectonically active regions, including subduction zones, antigorite-bearing rocks may persist to greater depths than other serpentine members. It often occurs as massive aggregates, layered sheets, or elongated crystals, and is frequently associated with talc, chlorite, magnetite, and quartz.

Physical properties

Antigorite is typically green to olive-green in color, with a pearly to silky luster on cleavage surfaces. It is translucent to opaque and has a Mohs hardness around 3–4. Its specific gravity is about 2.55. The mineral shows imperfect cleavage and commonly forms lamellar, foliated, or platy habits consistent with its sheet silicate structure. It is not a common source of asbestos; chrysotile, another serpentine member, is the form more historically associated with asbestos production.

Etymology

The name antigorite derives from a locality historically associated with its description, reflecting its origins in the Antigor region.

Notes

Antigorite distinguishes itself from other serpentine minerals by its stability range and characteristic X-ray diffraction pattern, making it a key indicator mineral in high-pressure, subduction-zone geology.