Ferro-hornblende is a complex iron-rich amphibole mineral often found in igneous and metamorphic terrains. Collectors identify it by its characteristic prismatic crystal habit and perfect cleavage angles, which distinguish it from pyroxenes like augite.
Is this ferro-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 ferro-hornblende with a known reference. Ferro-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. Ferro-hornblende leaves a grayish white streak.
- 3Read the lusterHold the specimen under a strong light. Ferro-hornblende typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark green, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive, fibrous.
Often confused with
Ferro-hornblende vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Ferro-hornblende leaves grayish white, Actinolite leaves white; luster reads vitreous on Ferro-hornblende and vitreous to silky on Actinolite.
How to tell apart: Streak differs — Ferro-hornblende leaves grayish white, Arfvedsonite leaves grey to bluish-grey.
Often found alongside ferro-hornblende
Minerals reported to co-occur with ferro-hornblende. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Fe₄Fe(AlSi₇O₂₂)(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.2-3.4 g/cm³
- Streak
- Grayish White
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Massive, Fibrous
- Cleavage
- Perfect in Two Directions At 56 and 124 Degrees
- Rarity
- Common
- Uses
- Collector, Petrological Research
- Host rock
- Igneous and Metamorphic Rocks Like Granite, Diorite, And Amphibolite
- Typical price
- $5-30 for representative specimens
Where rockhounds find ferro-hornblende
Classic worldwide localities
- Norway
- Sweden
- Canada
- USA
- Germany
Field-hunting tip
Look in igneous and metamorphic rocks like granite, diorite, and amphibolite country — that is the host setting where ferro-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, massive, fibrous habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferro-hornblende?+
Where is ferro-hornblende found?+
How much is ferro-hornblende worth?+
What rocks look like ferro-hornblende?+
What minerals are found with ferro-hornblende?+
What kind of rock does ferro-hornblende form in?+
What is ferro-hornblende used for?+
Find ferro-hornblende on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
