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 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale pink.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: light pink, dark pink, red.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic.
Often confused with
Wendwilsonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Wendwilsonite leaves pale pink, Roselite leaves light red.
How to tell apart: Talmessite is the harder of the two (Mohs 5 vs. 3-4); streak differs, so Wendwilsonite leaves pale pink, Talmessite leaves white.
How to tell apart: Luster reads vitreous on Wendwilsonite and subadamantine, pearly on cleavages 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
- 3-4
- Density
- 3.52 g/cm³
- Colors
- Streak
- Pale pink
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in cobalt-bearing hydrothermal mineral deposits
Where rockhounds find wendwilsonite
Classic worldwide localities
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
- Bou Azzer, Morocco
- An unknown locality in Coahuila, Mexico
Field-hunting tip
Where it forms: A rare secondary mineral in cobalt-bearing hydrothermal mineral deposits. If you start seeing talmessite, erythrite in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
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Find wendwilsonite on the map
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