Ferri-fluoro-katophorite is a rare member of the complex amphibole group, typically found in alkaline igneous environments. Collectors identify it by its dark, prismatic habit and specific associations with nepheline syenite assemblages. Due to its chemical complexity, professional analysis is often required for definitive identification compared to other members of the amphibole supergroup.
Is this ferri-fluoro-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 ferri-fluoro-katophorite with a known reference. Ferri-fluoro-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. Ferri-fluoro-katophorite leaves a white to light gray streak.
- 3Read the lusterHold the specimen under a strong light. Ferri-fluoro-katophorite typically shows a vitreous to sub-metallic luster.
- 4Match the color rangeCompare against the expected color range: dark green, black, brownish-black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, acicular aggregates, massive.
Often confused with
Ferri-fluoro-katophorite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Ferri-fluoro-katophorite leaves white to light gray, Hornblende leaves grayish-white; luster reads vitreous to sub-metallic on Ferri-fluoro-katophorite and vitreous on Hornblende.
How to tell apart: Streak differs — Ferri-fluoro-katophorite leaves white to light gray, Arfvedsonite leaves grey to bluish-grey; luster reads vitreous to sub-metallic on Ferri-fluoro-katophorite and vitreous on Arfvedsonite.
How to tell apart: Streak differs — Ferri-fluoro-katophorite leaves white to light gray, Riebeckite leaves blue-gray; luster reads vitreous to sub-metallic on Ferri-fluoro-katophorite and vitreous on Riebeckite.
Often found alongside ferri-fluoro-katophorite
Minerals reported to co-occur with ferri-fluoro-katophorite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na(NaCa)(Mg₄Fe³⁺)(AlSi₇O₂₂)(OH,F)₂
- Mohs hardness
- 5-6
- Density
- 3.3-3.5 g/cm³
- Streak
- White to Light Gray
- Luster
- Vitreous to Sub-metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Acicular Aggregates, Massive
- Cleavage
- Perfect Prismatic {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks, Syenites, Nepheline Syenites
- Typical price
- $20-150 for specimens
Where rockhounds find ferri-fluoro-katophorite
Classic worldwide localities
- Norway
- Canada
- Russia
- Sweden
Field-hunting tip
Look in alkaline igneous rocks, syenites, nepheline syenites country — that is the host setting where ferri-fluoro-katophorite typically forms. If you start seeing nepheline, aegirine, albite in float, you are in the right ground. Field specimens usually show a prismatic crystals, acicular aggregates, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferri-fluoro-katophorite?+
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Find ferri-fluoro-katophorite on the map
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