Willemseite is a nickel-rich member of the serpentine group often mistaken for fine-grained chrysoprase or talc. It typically occurs as dense, massive, apple-green platy aggregates associated with nickel-laterite deposits.
Is this willemseite?
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 willemseite with a known reference. Willemseite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: greenish white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: light green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy, massive, fine-grained aggregates.
Often confused with
Willemseite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Willemseite leaves greenish white, Serpentine leaves white; luster reads pearly on Willemseite and greasy on Serpentine.
How to tell apart: Chrysoprase is the harder of the two (Mohs 6.5-7 vs. 2); streak differs, so Willemseite leaves greenish white, Chrysoprase leaves white; luster reads pearly on Willemseite and vitreous to waxy on Chrysoprase.
Often found alongside willemseite
Minerals reported to co-occur with willemseite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ni₃Si₄O₁₀(OH)₂
- Mohs hardness
- 2
- Density
- 3.31 g/cm³
- Colors
- Streak
- Greenish white
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy, massive, fine-grained aggregates
- Cleavage
- {001}, perfect
- Rarity
- Rare
- Uses
- Collector, Scientific reference
- Host rock
- A secondary mineral in a nickel-bearing layered igneous sill
Where rockhounds find willemseite
Classic worldwide localities
- Found three km west of the Scotia talc mine, Bon Accord area, Barberton, Transvaal, South Africa
Field-hunting tip
Where it forms: A secondary mineral in a nickel-bearing layered igneous sill. If you start seeing ferroan trevorite, nimite, violarite in float, you are in the right ground. Typical habit: platy, massive, fine-grained aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify willemseite?+
Where is willemseite found?+
Is willemseite safe to handle?+
What rocks look like willemseite?+
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Find willemseite on the map
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