Actinolite

Actinolite is a calcium-bearing amphibole with compositions between magnesium-rich tremolite and iron-rich ferro-actinolite. It commonly forms green, elongated crystals and occurs in metamorphic rocks.

Amphibole: Amphiboles are a group of inosilicate minerals built from double chains of silicate tetrahedra. Actinolite belongs to this mineral group and shares its characteristic double-chain structure.
Greenschist facies: Greenschist facies is a metamorphic condition range commonly marked by chlorite, epidote, and actinolite. Actinolite is a characteristic mineral in many rocks metamorphosed under these conditions.
Actinolite asbestos: Actinolite asbestos is the fibrous habit of actinolite, consisting of separable elongated mineral fibers. Some actinolite forms fibers that can become airborne and pose serious health risks.
Greenschist: Greenschist is a metamorphic rock whose green color commonly comes from chlorite, epidote, and actinolite. Actinolite is a frequent source of the rock’s green color and a defining assemblage mineral.
Tremolite: Tremolite is the magnesium-rich calcium amphibole end member of the tremolite–actinolite series. It marks the magnesium-rich end of the compositional range that includes actinolite.
Metamorphism: Metamorphism is the mineralogical and textural alteration of rock by heat, pressure, and chemically active fluids. Actinolite commonly forms through mineral reactions during regional or contact metamorphism.
Asbestosis: Asbestosis is a chronic lung disease caused by inhaling asbestos fibers, leading to scarring of lung tissue. Inhaled actinolite-asbestos fibers can contribute to this disease.
Blueschist: Blueschist is a high-pressure, low-temperature metamorphic rock commonly containing glaucophane. Its characteristic high-pressure minerals contrast with actinolite-bearing greenschist assemblages.
Ferro-actinolite: Ferro-actinolite is the iron-rich calcium amphibole end member of the tremolite–actinolite series. It marks the iron-rich end of actinolite’s compositional series.
Subduction zone: A subduction zone is a region where one tectonic plate descends beneath another into the mantle. Water released from descending oceanic crust helps drive metamorphic reactions that can produce actinolite.

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