Actinolite prisms are characteristically long, slender, and often deeply striated monoclinic crystals ranging from pale to dark green. They are commonly found in metamorphic environments like greenschist facies or contact metamorphic zones, often embedded in talc or marble matrix.
Is this actinolite prisms?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch actinolite prisms with a known reference. Actinolite Prisms sits at Mohs 5.5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Actinolite Prisms leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Actinolite Prisms typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: bright green, dark green, blackish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, acicular, fibrous.
Often confused with
Actinolite Prisms vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside actinolite prisms
Minerals reported to co-occur with actinolite prisms. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂
- Mohs hardness
- 5.5-6
- Density
- 3.0-3.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Acicular, Fibrous
- Cleavage
- Perfect in Two Directions
- Rarity
- Common
- Uses
- Collector, Lapidary
- Host rock
- Metamorphic Rocks
- Typical price
- $10-100 depending on specimen size and clarity
Where rockhounds find actinolite prisms
1 mapped spotsClassic worldwide localities
- Ontario, Canada
- Zillertal, Austria
- Madagascar
- Switzerland
- New York, USA
Field-hunting tip
Look in metamorphic rocks country — that is the host setting where actinolite prisms typically forms. If you start seeing quartz, talc, calcite in float, you are in the right ground. Field specimens usually show a prismatic crystals, acicular, fibrous habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California — start trip planning there.
Common questions
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Find actinolite prisms on the map
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