Wendwilsonite is a rare calcium-magnesium arsenate that typically forms vibrant magenta to pink prismatic crystal clusters. It is best known from the Bou Azzer district in Morocco, where it occurs in hydrothermal veins associated with cobalt mineralization.
Is this wendwilsonite?
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 wendwilsonite with a known reference. Wendwilsonite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Wendwilsonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Wendwilsonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: pink, magenta.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular to prismatic crystals, often as radial sprays.
Often confused with
Wendwilsonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Talmessite is the harder of the two (Mohs 5 vs. 3.5).
How to tell apart: Wendwilsonite is noticeably harder (Mohs 3.5 vs. 1.5-2.5); streak differs — Wendwilsonite leaves white, Erythrite leaves pale pink; luster reads vitreous on Wendwilsonite and adamantine to pearly on Erythrite.
Often found alongside wendwilsonite
Minerals reported to co-occur with wendwilsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Mg(AsO₄)₂·2H₂O
- Mohs hardness
- 3.5
- Density
- 3.56 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular to Prismatic Crystals, Often as Radial Sprays
- Cleavage
- Good On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Serpentinite
- Typical price
- $50-300 thumbnail
Where rockhounds find wendwilsonite
Classic worldwide localities
- Bou Azzer, Morocco
- Tsumeb, Namibia
Field-hunting tip
Look in hydrothermal veins in serpentinite country — that is the host setting where wendwilsonite typically forms. If you start seeing dolomite, quartz, cobaltite in float, you are in the right ground. Field specimens usually show a acicular to prismatic crystals, often as radial sprays habit, so train your eye for that shape before scanning the outcrop.
Common questions
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