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, so 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, so 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, so 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, 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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