Wilkinsonite is a very rare member of the aenigmatite group typically found as dark, opaque crystals in alkaline igneous environments. It is most notable for being found in high-alkaline pegmatite complexes like those at Mont Saint-Hilaire, often appearing as dark, lustrous prismatic clusters.
Is this wilkinsonite?
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 wilkinsonite with a known reference. Wilkinsonite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Wilkinsonite leaves a brownish black streak.
- 3Read the lusterHold the specimen under a strong light. Wilkinsonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: triclinic. Typical habit: prismatic crystals, anhedral grains.
Often confused with
Wilkinsonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Wilkinsonite leaves brownish black, Aenigmatite leaves reddish-brown.
How to tell apart: Streak differs, so Wilkinsonite leaves brownish black, Hornblende leaves grayish-white.
How to tell apart: Streak differs, so Wilkinsonite leaves brownish black, Arfvedsonite leaves grey to bluish-grey.
Often found alongside wilkinsonite
Minerals reported to co-occur with wilkinsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Fe²⁺₄Fe³⁺₂Si₆O₂₀
- Mohs hardness
- 5.5
- Density
- 3.55 g/cm³
- Colors
- Streak
- Brownish Black
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Prismatic Crystals, Anhedral Grains
- Cleavage
- Distinct On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Nepheline Syenite Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find wilkinsonite
Classic worldwide localities
- Mont Saint-Hilaire, Quebec, Canada
- Kola Peninsula, Russia
Field-hunting tip
Look in nepheline syenite pegmatites country, the host setting where wilkinsonite typically forms. If you start seeing nepheline, microcline, aegirine in float, you are in the right ground. Field specimens usually show a prismatic crystals, anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find wilkinsonite on the map
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