Green amphibole, typically representing members of the hornblende series, is characterized by its distinct prismatic crystal habit and perfect cleavage at near-60 and 120-degree angles. It is a widespread constituent of metamorphic rocks, often forming elongated, dark green blades that are easily recognizable in hand specimens.
Is this green amphibole?
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 green amphibole with a known reference. Green Amphibole sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Green Amphibole leaves a white to pale green streak.
- 3Read the lusterHold the specimen under a strong light. Green Amphibole typically shows a vitreous to pearly luster.
- 4Match the color rangeCompare against the expected color range: green, dark green, blackish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, acicular, fibrous, massive.
Often confused with
Green Amphibole vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Green Amphibole leaves white to pale green, Pyroxene leaves white to grey; luster reads vitreous to pearly on Green Amphibole and vitreous to dull on Pyroxene.
How to tell apart: Tourmaline is the harder of the two (Mohs 7-7.5 vs. 5-6); streak differs, so Green Amphibole leaves white to pale green, Tourmaline leaves white; luster reads vitreous to pearly on Green Amphibole and vitreous on Tourmaline.
How to tell apart: Streak differs, so Green Amphibole leaves white to pale green, Epidote leaves white; luster reads vitreous to pearly on Green Amphibole and vitreous on Epidote.
Often found alongside green amphibole
Minerals reported to co-occur with green amphibole. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂(Mg,Fe²⁺)₅Si₈O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.0-3.5 g/cm³
- Streak
- White to Pale Green
- Luster
- Vitreous to Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Acicular, Fibrous, Massive
- Cleavage
- Perfect in Two Directions At 56 and 124 Degrees
- Rarity
- Common
- Uses
- Collector, Geological Study
- Host rock
- Metamorphic Rocks Like Amphibolites and Schists, Also in Igneous Rocks
- Typical price
- $5-50 thumbnail
Where rockhounds find green amphibole
1 mapped spotsClassic worldwide localities
- Ontario, Canada
- New York, USA
- Valais, Switzerland
- Norway
- Russia
Field-hunting tip
Look in metamorphic rocks like amphibolites and schists, also in igneous rocks country, the host setting where green amphibole typically forms. If you start seeing calcite, quartz, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, acicular, fibrous, massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in West Virginia. Start trip planning there.
Common questions
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Find green amphibole on the map
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