Magnesio-arfvedsonite is a rare member of the amphibole supergroup typically found in alkaline igneous environments. It usually occurs as dark, prismatic to acicular crystals often associated with other rare alkaline minerals in syenite complexes.
Is this magnesio-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-arfvedsonite with a known reference. Magnesio-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-arfvedsonite leaves a greyish streak.
- 3Read the lusterHold the specimen under a strong light. Magnesio-arfvedsonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark green, dark blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, acicular, fibrous, columnar.
Often confused with
Magnesio-arfvedsonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Magnesio-arfvedsonite leaves greyish, Arfvedsonite leaves grey to bluish-grey.
How to tell apart: Streak differs — Magnesio-arfvedsonite leaves greyish, Riebeckite leaves blue-gray.
How to tell apart: Streak differs — Magnesio-arfvedsonite leaves greyish, Hornblende leaves grayish-white.
Often found alongside magnesio-arfvedsonite
Minerals reported to co-occur with magnesio-arfvedsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaNa₂(Mg₄Fe³⁺)Si₈O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.3-3.5 g/cm³
- Colors
- Streak
- Greyish
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Acicular, Fibrous, Columnar
- Cleavage
- Perfect Prismatic
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks, Pegmatites, Syenites
- Typical price
- $20-150 for thumbnail to small cabinet specimens
Where rockhounds find magnesio-arfvedsonite
Classic worldwide localities
- Mont Saint-Hilaire, Canada
- Norra Kärr, Sweden
- Kola Peninsula, Russia
- Magnet Cove, USA
Field-hunting tip
Look in alkaline igneous rocks, pegmatites, syenites country — that is the host setting where magnesio-arfvedsonite typically forms. If you start seeing nepheline, aegirine, microcline in float, you are in the right ground. Field specimens usually show a prismatic crystals, acicular, fibrous, columnar habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify magnesio-arfvedsonite?+
Where is magnesio-arfvedsonite found?+
How much is magnesio-arfvedsonite worth?+
What rocks look like magnesio-arfvedsonite?+
What minerals are found with magnesio-arfvedsonite?+
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Find magnesio-arfvedsonite on the map
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