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. Streak: white to pale gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to pearly.
- 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, Augite leaves gray-green.
How to tell apart: Streak differs, so Green Hornblende leaves white to pale gray, Arfvedsonite leaves deep bluish gray, gray-green.
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
Where rockhounds find green hornblende
1 mapped spotsClassic worldwide localities
- Ontario, Canada
- New York, USA
- Norway
- Finland
- Italy
Field-hunting tip
Where it forms: igneous and metamorphic rocks. If you start seeing quartz, plagioclase, biotite in float, you are in the right ground. Typical habit: prismatic crystals, elongated, bladed, massive. 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
How do you identify green hornblende?+
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What rocks look like green hornblende?+
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Find green hornblende on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
