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. Streak: light green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: dark 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, so Pecoraite leaves light green, Chrysotile leaves white; luster reads vitreous on Pecoraite and silky on Chrysotile.
How to tell apart: Streak differs, so Pecoraite leaves light green, Annabergite leaves pale green to white; luster reads vitreous on Pecoraite and subadamantine, pearly on cleavages, may be dull, earthy 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
- 3.084 g/cm³
- Colors
- Streak
- Light green
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, matted aggregates, earthy crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed by weathering of Ni-Fe meteorite fragments in a desert environment (Wolf Creek meteorite); along shears in Archaean ultramafic rocks (Otway prospect, Western Australia); in geodes (St. Louis, Missouri, USA)
Where rockhounds find pecoraite
Classic worldwide localities
- Otway prospect, near Spinnaway, Nullagine district, and in Rocky's Reward pit, near Agnew, Western Australia
- Tscheremschanskoe, Ural Mountains, Russia
Field-hunting tip
Where it forms: Formed by weathering of Ni-Fe meteorite fragments in a desert environment (Wolf Creek meteorite); along shears in Archaean ultramafic rocks (Otway prospect, Western Australia); in geodes (St. Louis, Missouri, USA). If you start seeing maghemite, quartz, goethite in float, you are in the right ground. Typical habit: fibrous, matted aggregates, earthy crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pecoraite?+
Where is pecoraite found?+
Is pecoraite safe to handle?+
What rocks look like pecoraite?+
What minerals are found with pecoraite?+
What kind of rock does pecoraite form in?+
What is pecoraite used for?+
Find pecoraite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
