Green hornblende is a common rock-forming amphibole found in a wide variety of igneous and metamorphic environments. It is characterized by its distinct dark green to black-green color and its tendency to form elongated, prismatic crystals with characteristic 56 and 124-degree cleavage angles.
Is this green hornblende?
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 hornblende with a known reference. Green Hornblende 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 Hornblende leaves a white to pale gray streak.
- 3Read the lusterHold the specimen under a strong light. Green Hornblende typically shows a vitreous to pearly luster.
- 4Match the color rangeCompare against the expected color range: dark green, blackish green, brownish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, elongated, bladed, massive.
Often confused with
Green Hornblende vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Green Hornblende leaves white to pale gray, Actinolite leaves white; luster reads vitreous to pearly on Green Hornblende and vitreous to silky on Actinolite.
How to tell apart: Streak differs — Green Hornblende leaves white to pale gray, Augite leaves grayish white; luster reads vitreous to pearly on Green Hornblende and vitreous on Augite.
How to tell apart: Streak differs — Green Hornblende leaves white to pale gray, Arfvedsonite leaves grey to bluish-grey; luster reads vitreous to pearly on Green Hornblende and vitreous on Arfvedsonite.
Often found alongside green hornblende
Minerals reported to co-occur with green hornblende. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Na)₂₋₃(Mg,Fe,Al)₅Si₆(Si,Al)₂O₂₂(OH,F)₂
- Mohs hardness
- 5-6
- Density
- 3.0-3.4 g/cm³
- Streak
- White to Pale Gray
- Luster
- Vitreous to Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Elongated, Bladed, Massive
- Cleavage
- Perfect in Two Directions At 56 and 124 Degrees
- Rarity
- Common
- Uses
- Collector, Geological Indicator
- Host rock
- Igneous and Metamorphic Rocks
- Typical price
- $5-50 for hand specimens
Where rockhounds find green hornblende
1 mapped spotsClassic worldwide localities
- Ontario, Canada
- New York, USA
- Norway
- Finland
- Italy
Field-hunting tip
Look in igneous and metamorphic rocks country — that is the host setting where green hornblende typically forms. If you start seeing quartz, plagioclase, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, elongated, bladed, massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in South Carolina — start trip planning there.
Common questions
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Find green hornblende on the map
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