Ferro-ferri-hornblende is a member of the complex amphibole group, typically appearing as dark, elongated prismatic crystals. It is primarily found in metamorphic environments and certain igneous intrusions, identified by its distinct cleavage angles. Collectors typically identify this mineral through X-ray diffraction or electron microprobe analysis due to its similarity to other hornblende species.

Hardness

5-6

Mohs

Luster

Vitreous

Transparency

Transparent

mineraluncommonAmphibole Group family

Ferro-ferri-hornblende

Hardness: 5-6
Luster: Vitreous
Transparency: Transparent

Is this ferro-ferri-hornblende?

4-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch ferro-ferri-hornblende with a known reference. Ferro-ferri-hornblende sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
3
Match the color range
Compare against the expected color range: dark green.
4
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, fibrous, columnar, or massive.

Often confused with

Ferro-ferri-hornblende vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside ferro-ferri-hornblende

Minerals reported to co-occur with ferro-ferri-hornblende. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Ca₂Fe²⁺₄Fe³⁺(Si₇Al)O₂₂(OH)₂
Mohs hardness: 5-6
Density: 3.362 g/cm³
Colors: Dark green
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic crystals, fibrous, columnar, or massive
Cleavage: Perfect on {110}
Rarity: Uncommon
Uses: Collector, Scientific research
Host rock: In a contact metamorphic rock (skarn)

Where rockhounds find ferro-ferri-hornblende

Classic worldwide localities

Traversella iron mine, Val Chiusella, Ivrea, Piemonte, Italy

Field-hunting tip

Where it forms: In a contact metamorphic rock (skarn). If you start seeing tremolite, hastingsite, magnesio-hastingsite in float, you are in the right ground. Typical habit: prismatic crystals, fibrous, columnar, or massive. Train your eye for that shape before scanning the outcrop.

More ferro-ferri-hornblende photos

Common questions

How do you identify ferro-ferri-hornblende?+

Mohs hardness is 5-6. Luster: vitreous. Common colors include dark green.

Where is ferro-ferri-hornblende found?+

Notable localities include Traversella iron mine, Val Chiusella, Ivrea, Piemonte, Italy.

What rocks look like ferro-ferri-hornblende?+

Ferro-ferri-hornblende is most often confused with Hornblende, Actinolite, Arfvedsonite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with ferro-ferri-hornblende?+

Ferro-ferri-hornblende commonly co-occurs with Tremolite, Hastingsite, Magnesio-hastingsite, Quartz, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ferro-ferri-hornblende form in?+

Where it forms: In a contact metamorphic rock (skarn). Working float back to the host body is the standard way to chase a fresh occurrence.

What is ferro-ferri-hornblende used for?+

Ferro-ferri-hornblende is used in collector, scientific research.

Find ferro-ferri-hornblende on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.