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 — Wilkinsonite leaves brownish black, Aenigmatite leaves reddish-brown.
How to tell apart: Streak differs — Wilkinsonite leaves brownish black, Hornblende leaves grayish-white.
How to tell apart: Streak differs — 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 — that is 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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