Actinolite
Actinolite is inosilicate (amphibole), Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂. In the hand, it rates 5 to 6 on the Mohs scale, and it runs green and gray-green. Grass-to-bottle-green bladed or needle-like crystals in radiating sprays, with the two diagonal amphibole cleavages. Greenschists and altered mafic rocks; notable: Austria, China, Russia, Vermont (USA); gem needles-in-quartz from Brazil.
The geology.
Actinolite carries the formula Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂. It belongs to the monoclinic system. It is classified as inosilicate (amphibole).
It sits at 5 to 6 on the Mohs scale. The surface reads vitreous to silky. Light behaviour is transparent to opaque. Specific gravity runs 3.0 to 3.2. The streak is white. It breaks with two perfect cleavages at ~56°/124°; splintery.
Grass-to-bottle-green bladed or needle-like crystals in radiating sprays, with the two diagonal amphibole cleavages.
You will most often meet it as bladed sprays, radiating needles, fibrous masses or needles in quartz crystals.
The origins.
Greenschists and altered mafic rocks; notable: Austria, China, Russia, Vermont (USA); gem needles-in-quartz from Brazil.
On value, the database notes: common; gemmy green needles in clear quartz are mid-range.
Traditional associations.
In energy work traditions, associated with steady expansion and shielding during change.
People buy on this language, so it belongs on the page. It belongs under the facts, though, not over them.
Spotting the real thing.
Grass-to-bottle-green bladed or needle-like crystals in radiating sprays, with the two diagonal amphibole cleavages.
| Looks like | How to tell them apart |
|---|---|
| Epidote | Epidote is pistachio yellow-green; actinolite is purer to grayer green |
| Green tourmaline | Tourmaline is harder with rounded-triangle striated prisms |
| Diopside | Pyroxene cleavages meet near 90°; amphibole cleavages meet near 56°/124° |
At-home tests.
You can run every one of these at a kitchen table. Good light matters more than gear when you are looking at actinolite.
| Test | What you should see |
|---|---|
| Scratch check | Knife scratches it with effort (Mohs 5 to 6) |
| By eye | Splintery bladed habit |
| By eye | Cleavage faces meet at oblique amphibole angles |
Stop short of anything that leaves a mark. A gemologist can answer the rest without damaging the stone.
Care & handling.
At 5 to 6 on the Mohs scale it handles careful wear but scratches against quartz and dust. Store it separately and take rings off before rough work.
It breaks with two perfect cleavages at ~56°/124°; splintery, which is worth knowing before you set it or drop it.
Skip the ultrasonic. Lukewarm water, mild soap and a soft cloth handle routine cleaning without risk.
Fibrous asbestiform actinolite is a regulated asbestos, solid crystals and polished stones are safe to handle, but never crush, sand, or breathe dust from fibrous material.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂. Crystal system: Monoclinic. Specific gravity: 3.0 to 3.2. Streak: White. Cleavage and fracture: Two perfect cleavages at ~56°/124°; splintery.
How it reaches the market
Greenschists and altered mafic rocks; notable: Austria, China, Russia, Vermont (USA); gem needles-in-quartz from Brazil.
What it gets confused with
Epidote: Epidote is pistachio yellow-green; actinolite is purer to grayer green. Green tourmaline: Tourmaline is harder with rounded-triangle striated prisms. Diopside: Pyroxene cleavages meet near 90°; amphibole cleavages meet near 56°/124°.
What it is worth
Common; gemmy green needles in clear quartz are mid-range.
One more thing
Nephrite jade is actinolite's fibers felted so tightly the mineral becomes tougher than steel against shattering.
An education-first guide.
We do not carry actinolite. This page exists because the question comes up and the honest answer is worth writing down, whether or not there is anything here to sell you.
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