Ferro-ferri-nybøite is a rare member of the amphibole supergroup typically found in alkaline igneous complexes. Collectors usually identify it as dark, prismatic crystals embedded within nepheline syenites or associated pegmatites. It is highly valued for its mineralogical rarity and specific chemical composition.
Is this ferro-ferri-nybøite?
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-nybøite with a known reference. Ferro-ferri-nybøite sits at Mohs ~6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish green to black.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: jet-black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Ferro-ferri-nybøite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferro-ferri-nybøite leaves grayish green to black, Arfvedsonite leaves deep bluish gray, gray-green.
How to tell apart: Streak differs, so Ferro-ferri-nybøite leaves grayish green to black, Riebeckite leaves greenish brown.
How to tell apart: Streak differs, so Ferro-ferri-nybøite leaves grayish green to black, Magnesio-riebeckite leaves blue-gray.
Often found alongside ferro-ferri-nybøite
Minerals reported to co-occur with ferro-ferri-nybøite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaNa₂(Fe₃Fe₂)(Si₇Al)O₂₂(OH)₂
- Mohs hardness
- ~6
- Density
- 3.424 g/cm³
- Colors
- Jet-black
- Streak
- Grayish green to black
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals
- Cleavage
- Perfect on {110}, (planes intersecting at ~ 56°)
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- The earliest mineral in an igneous microbreccia in an alkaline syenite-gabbro complex
Where rockhounds find ferro-ferri-nybøite
Classic worldwide localities
- Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie (formerly Rouville County), Québec, Canada
Field-hunting tip
Where it forms: The earliest mineral in an igneous microbreccia in an alkaline syenite-gabbro complex. If you start seeing albite, nepheline in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferro-ferri-nybøite?+
Where is ferro-ferri-nybøite found?+
What rocks look like ferro-ferri-nybøite?+
What minerals are found with ferro-ferri-nybøite?+
What kind of rock does ferro-ferri-nybøite form in?+
What is ferro-ferri-nybøite used for?+
Find ferro-ferri-nybøite on the map
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