Ferro-ferri-katophorite is a rare member of the complex calcic-sodic amphibole group found primarily in alkaline igneous environments. Collectors identify it by its dark, prismatic monoclinic crystal habit and its characteristic occurrence in syenites or nepheline-bearing complexes.

Hardness

5-6

Mohs

Luster

Vitreous

Transparency

Opaque

mineralrareAmphibole Supergroup family

Ferro-ferri-katophorite

Hardness: 5-6
Luster: Vitreous
Transparency: Opaque

Is this ferro-ferri-katophorite?

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-katophorite with a known reference. Ferro-ferri-katophorite 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: black, dark brown, dark green.
4
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, massive, granular.

Often confused with

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

Often found alongside ferro-ferri-katophorite

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

All properties

Chemical formula: Na(NaCa)(Fe²⁺₄Fe³⁺)(AlSi₇O₂₂)(OH)₂
Mohs hardness: 5-6
Density: 3.3-3.5 g/cm³
Colors: Black Dark brown Dark green
Luster: Vitreous
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Prismatic crystals, massive, granular
Rarity: Rare
Uses: Collector, Scientific research
Host rock: alkaline igneous rocks

Where rockhounds find ferro-ferri-katophorite

Classic worldwide localities

Kola Peninsula, Russia
Mont Saint-Hilaire, Canada
Norway
Sweden

Field-hunting tip

Where it forms: alkaline igneous rocks. If you start seeing nepheline, aegirine, microcline in float, you are in the right ground. Typical habit: prismatic crystals, massive, granular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ferro-ferri-katophorite?+

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

Where is ferro-ferri-katophorite found?+

Notable localities include Kola Peninsula, Russia; Mont Saint-Hilaire, Canada; Norway; Sweden.

What rocks look like ferro-ferri-katophorite?+

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

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

Ferro-ferri-katophorite commonly co-occurs with Nepheline, Aegirine, Microcline, Eudialyte. Spotting any of these in float or country rock is a useful trip signal.

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

Where it forms: alkaline igneous rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ferro-ferri-katophorite used for?+

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

Find ferro-ferri-katophorite on the map

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