Hornblende is a dark-colored amphibole mineral commonly found as a rock-forming constituent in many igneous and metamorphic environments. Collectors typically look for its characteristic prismatic crystal habit and the distinctive 56 and 124-degree cleavage angles that help distinguish it from pyroxenes like augite.
Is this 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 hornblende with a known reference. 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. Hornblende leaves a grayish-white streak.
- 3Read the lusterHold the specimen under a strong light. Hornblende typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark green, brownish-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, bladed, fibrous, or massive.
Often confused with
Hornblende vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Hornblende leaves grayish-white, Augite leaves grayish white.
How to tell apart: Streak differs — Hornblende leaves grayish-white, Arfvedsonite leaves grey to bluish-grey.
How to tell apart: Tourmaline is the harder of the two (Mohs 7-7.5 vs. 5-6); streak differs — Hornblende leaves grayish-white, Tourmaline leaves white.
Often found alongside hornblende
Minerals reported to co-occur with 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,Fe²⁺,Fe³⁺,Al)₅Si₆(Si,Al)₂O₂₂(OH,F)₂
- Mohs hardness
- 5-6
- Density
- 3.0-3.4 g/cm³
- Streak
- Grayish-white
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Bladed, Fibrous, Or Massive
- Cleavage
- Perfect in Two Directions At 56 and 124 Degrees
- Rarity
- Common
- Uses
- Collector, Petrology Study
- Host rock
- Igneous and Metamorphic Rocks Like Granite, Diorite, And Schist
- Typical price
- $5-30 for typical specimens
Where rockhounds find hornblende
16 mapped spotsClassic worldwide localities
- Vesuvius, Italy
- Ontario, Canada
- Franklin, New Jersey, USA
- Arendal, Norway
- Kola Peninsula, Russia
Field-hunting tip
Look in igneous and metamorphic rocks like granite, diorite, and schist country — that is the host setting where hornblende typically forms. If you start seeing quartz, feldspar, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, bladed, fibrous, or massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in North Carolina, Utah, Vermont — start trip planning there.
Common questions
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Find hornblende on the map
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