Petterdite is a rare lead chromate mineral that occurs as distinct, flattened hexagonal plates. It is a secondary mineral primarily found in oxidized zones of lead-rich hydrothermal ore deposits.
Is this petterdite?
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 petterdite with a known reference. Petterdite 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: pale violet.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly to earthy.
- 4Match the color rangeCompare against the expected color range: pale gray, pinkish violet.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: encrustations, platy.
Often confused with
Petterdite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Mimetite is the harder of the two (Mohs 3.5-4 vs. ~2); streak differs, so Petterdite leaves pale violet, Mimetite leaves white; luster reads pearly to earthy on Petterdite and resinous to subadamantine on Mimetite.
How to tell apart: Streak differs, so Petterdite leaves pale violet, Crocoite leaves yellow-orange; luster reads pearly to earthy on Petterdite and adamantine on Crocoite.
How to tell apart: Pyromorphite is the harder of the two (Mohs 3.5-4 vs. ~2); streak differs, so Petterdite leaves pale violet, Pyromorphite leaves white; luster reads pearly to earthy on Petterdite and resinous to subadamantine on Pyromorphite.
Often found alongside petterdite
Minerals reported to co-occur with petterdite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbCr₂(CO₃)₂(OH)₄·H₂O
- Mohs hardness
- ~2
- Density
- 3.947 g/cm³
- Colors
- Pale grayPinkish violet
- Streak
- Pale violet
- Luster
- Pearly to earthy
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Encrustations, platy
- Cleavage
- On {100}, fair; on {010}, possible
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary species probably formed by alteration of galena by Cr-bearing meteoric waters (Red Lead mine, Australia); in the oxidation zone of a hydrothermal vein cutting serpentinite (Callenberg mine, Germany)
Where rockhounds find petterdite
Classic worldwide localities
- Red Lead mine, Dundas, Tasmania, Australia
- Callenberg nickel mine, near Hohenstein-Ernstthal, Saxony, Germany
Field-hunting tip
Where it forms: A rare secondary species probably formed by alteration of galena by Cr-bearing meteoric waters (Red Lead mine, Australia); in the oxidation zone of a hydrothermal vein cutting serpentinite (Callenberg mine, Germany). If you start seeing anglesite, crocoite, limonite in float, you are in the right ground. Typical habit: encrustations, platy. Train your eye for that shape before scanning the outcrop.
Common questions
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Find petterdite on the map
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