Petewilliamsite is a very rare nickel arsenate mineral typically found as small, vibrant green crusts or tiny prismatic crystals. It is most often found in association with other rare arsenates in the oxidized zones of nickel-cobalt ore deposits.
Is this petewilliamsite?
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 petewilliamsite with a known reference. Petewilliamsite 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. Petewilliamsite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Petewilliamsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: green, blue-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: small prismatic crystals, druzy crusts.
Often confused with
Petewilliamsite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Petewilliamsite is noticeably harder (Mohs 3.5 vs. 1.5-2.5); luster reads vitreous on Petewilliamsite and pearly, vitreous on Annabergite.
How to tell apart: Petewilliamsite is noticeably harder (Mohs 3.5 vs. 1.5-2.5); streak differs — Petewilliamsite leaves pale green, Erythrite leaves pale pink; luster reads vitreous on Petewilliamsite and adamantine to pearly on Erythrite.
Often found alongside petewilliamsite
Minerals reported to co-occur with petewilliamsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ni,Co)₃(As₂O₈)
- Mohs hardness
- 3.5
- Density
- 4.49 g/cm³
- Colors
- Streak
- Pale Green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Small Prismatic Crystals, Druzy Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Ore Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find petewilliamsite
Classic worldwide localities
- Hagendorf-Sud, Germany
- Bou Azzer, Morocco
Field-hunting tip
Look in hydrothermal veins in ore deposits country — that is the host setting where petewilliamsite typically forms. If you start seeing annabergite, arsenolite, retgersite in float, you are in the right ground. Field specimens usually show a small prismatic crystals, druzy crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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