Pecoraite is a rare nickel-rich member of the serpentine group, often found as bright apple-green crusts or fibrous mats. It typically forms as an alteration product of nickel sulfides in weathered ultramafic environments. Collectors prize it for its intense, vibrant color, though it is usually found in small, delicate patches.
Is this pecoraite?
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 pecoraite with a known reference. Pecoraite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Pecoraite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Pecoraite typically shows a earthy luster.
- 4Match the color rangeCompare against the expected color range: bright green, apple green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, matted aggregates, earthy crusts.
Often confused with
Pecoraite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Pecoraite leaves pale green, Chrysotile leaves white; luster reads earthy on Pecoraite and silky on Chrysotile.
How to tell apart: Luster reads earthy on Pecoraite and pearly, vitreous on Annabergite.
Often found alongside pecoraite
Minerals reported to co-occur with pecoraite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ni₃Si₂O₅(OH)₄
- Mohs hardness
- 2.5
- Density
- 2.6-2.7 g/cm³
- Colors
- Streak
- Pale Green
- Luster
- Earthy
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Matted Aggregates, Earthy Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Nickel-bearing Ultramafic Rocks
- Typical price
- $20-150 for small micro-mounts or crust fragments
Where rockhounds find pecoraite
Classic worldwide localities
- Widgiemooltha, Australia
- New Idria District, USA
- Ghezzano, Italy
Field-hunting tip
Look in nickel-bearing ultramafic rocks country — that is the host setting where pecoraite typically forms. If you start seeing magnesite, goethite, quartz in float, you are in the right ground. Field specimens usually show a fibrous, matted aggregates, earthy crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find pecoraite on the map
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