Magnesio-fluoro-arfvedsonite is a rare amphibole-group mineral often found in alkaline igneous complexes. It typically presents as dark, prismatic to acicular crystals and requires laboratory testing, such as chemical analysis, to distinguish from other members of the arfvedsonite series.
Is this magnesio-fluoro-arfvedsonite?
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 magnesio-fluoro-arfvedsonite with a known reference. Magnesio-fluoro-arfvedsonite 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. Magnesio-fluoro-arfvedsonite leaves a grey streak.
- 3Read the lusterHold the specimen under a strong light. Magnesio-fluoro-arfvedsonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark blue, dark green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, fibrous, acicular.
Often confused with
Magnesio-fluoro-arfvedsonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Magnesio-fluoro-arfvedsonite leaves grey, Arfvedsonite leaves grey to bluish-grey.
How to tell apart: Streak differs — Magnesio-fluoro-arfvedsonite leaves grey, Riebeckite leaves blue-gray.
How to tell apart: Streak differs — Magnesio-fluoro-arfvedsonite leaves grey, Glaucophane leaves white.
Often found alongside magnesio-fluoro-arfvedsonite
Minerals reported to co-occur with magnesio-fluoro-arfvedsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaNa₂(Mg₄Fe³⁺)Si₈O₂₂F₂
- Mohs hardness
- 5-6
- Density
- 3.1-3.3 g/cm³
- Colors
- Streak
- Grey
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, Fibrous, Acicular
- Cleavage
- Perfect in Two Directions
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks, Nepheline Syenites, Pegmatites
- Typical price
- $20-150 for thumbnail to small cabinet specimens
Where rockhounds find magnesio-fluoro-arfvedsonite
Classic worldwide localities
- Mont Saint-Hilaire, Canada
- Kola Peninsula, Russia
- Norra Kärr, Sweden
Field-hunting tip
Look in alkaline igneous rocks, nepheline syenites, pegmatites country — that is the host setting where magnesio-fluoro-arfvedsonite typically forms. If you start seeing aegirine, nepheline, microcline in float, you are in the right ground. Field specimens usually show a prismatic, fibrous, acicular habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify magnesio-fluoro-arfvedsonite?+
Where is magnesio-fluoro-arfvedsonite found?+
How much is magnesio-fluoro-arfvedsonite worth?+
What rocks look like magnesio-fluoro-arfvedsonite?+
What minerals are found with magnesio-fluoro-arfvedsonite?+
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