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.
Is this ferro-ferri-katophorite?
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-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.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ferro-ferri-katophorite leaves a grayish white streak.
- 3Read the lusterHold the specimen under a strong light. Ferro-ferri-katophorite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown, dark green.
- 5Look at form & habitCrystal 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.
How to tell apart: Streak differs — Ferro-ferri-katophorite leaves grayish white, Hornblende leaves grayish-white.
How to tell apart: Streak differs — Ferro-ferri-katophorite leaves grayish white, Arfvedsonite leaves grey to bluish-grey.
How to tell apart: Streak differs — Ferro-ferri-katophorite leaves grayish white, Riebeckite leaves blue-gray.
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
- Streak
- Grayish White
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Massive, Granular
- Cleavage
- Perfect in Two Directions
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Alkaline Igneous Rocks
- Typical price
- $20-100 thumbnail
Where rockhounds find ferro-ferri-katophorite
Classic worldwide localities
- Kola Peninsula, Russia
- Mont Saint-Hilaire, Canada
- Norway
- Sweden
Field-hunting tip
Look in alkaline igneous rocks country — that is the host setting where ferro-ferri-katophorite typically forms. If you start seeing nepheline, aegirine, microcline in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ferro-ferri-katophorite on the map
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