Paulkellerite is a very rare secondary bismuth iron phosphate found in oxidized zones. It typically forms small, vibrant yellow to yellow-green tabular or bladed crystals and is a highly sought-after species for micromount collectors due to its extreme scarcity.
Is this paulkellerite?
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 paulkellerite with a known reference. Paulkellerite sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: very pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to adamantine.
- 4Match the color rangeCompare against the expected color range: greenish yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: bladed to tabular crystals.
Often confused with
Paulkellerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Paulkellerite is noticeably harder (Mohs ~4 vs. 2-2.5); streak differs, so Paulkellerite leaves very pale yellow, Autunite leaves pale yellow.
How to tell apart: Paulkellerite is noticeably harder (Mohs ~4 vs. 2-2.5); streak differs, so Paulkellerite leaves very pale yellow, Meta-autunite leaves yellow; luster reads vitreous to adamantine on Paulkellerite and pearly to dull on Meta-autunite.
Often found alongside paulkellerite
Minerals reported to co-occur with paulkellerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₂Fe³⁺O₂(PO₄)(OH)₂
- Mohs hardness
- ~4
- Density
- 6.23 g/cm³
- Colors
- Streak
- Very pale yellow
- Luster
- Vitreous to adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Bladed to tabular crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in Bi–Ni–Co ores in a hydrothermal ore deposit
Where rockhounds find paulkellerite
Classic worldwide localities
- Neuhilfe mine, Schneeberg, Saxony, Germany
Field-hunting tip
Where it forms: A rare secondary mineral in Bi–Ni–Co ores in a hydrothermal ore deposit. If you start seeing bismuth, skutterudite, pyrite in float, you are in the right ground. Typical habit: bladed to tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find paulkellerite on the map
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