mineral

Actinolite (likely fibrous amphibole)

Actinolite, Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂; possibly an actinolite–tremolite specimen

AI-generated identification · may be incorrect

Pale green to gray-green, silky to vitreous luster, strongly fibrous/bladed crystals with lengthwise cleavage; Mohs hardness 5–6, monoclinic amphibole structure, specific gravity about 3.0–3.4. The image suggests a natural, unpolished specimen.

Identified August 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly during low- to medium-grade regional or contact metamorphism of magnesium- and iron-rich rocks, commonly replacing pyroxene or occurring in serpentinite, schist, and metamorphosed basalt. Most examples are geologically Paleozoic or younger, though the mineral forms across many ages.

Uses & applications

Used chiefly as a collector mineral; compact, attractive material may be cut into cabochons or ornamental objects. Fibrous amphiboles should not be cut, crushed, or inhaled because some varieties can produce hazardous mineral dust.

Geological facts

Its long, splintery crystals and green color distinguish it from massive green serpentine and mica. Actinolite is the iron-rich member of the tremolite–actinolite series.

Field identification & locations

Look for green, radiating or parallel fibers, amphibole cleavage, and hardness sufficient to scratch glass; a streak, density test, and Raman/XRD analysis can confirm it. Common localities include Austria, Switzerland, Italy, Pakistan, China, and the United States.