Stefanweissite is a rare calcium zirconium niobium oxide that forms flattened prismatic crystals. It occurs in cavities inside sanidinite volcanic ejecta. It was first described from In den Dellen (Zieglowski) pumice quarry, Eifel region, Rhineland-Palatinate, Germany.
Is this stefanweissite?
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 stefanweissite with a known reference. Stefanweissite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light brown to yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: brown, reddish brown, dark brownish red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: flattened prismatic crystals.
Often confused with
Stefanweissite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Gorceixite is the harder of the two (Mohs 6 vs. 4.5); streak differs, so Stefanweissite leaves light brown to yellow, Gorceixite leaves white; luster reads adamantine on Stefanweissite and vitreous on Gorceixite.
How to tell apart: Stefanweissite is noticeably harder (Mohs 4.5 vs. ~2); streak differs, so Stefanweissite leaves light brown to yellow, Schulenbergite leaves blue-green, pale green; luster reads adamantine on Stefanweissite and vitreous, pearly on {0001} on Schulenbergite.
Often found alongside stefanweissite
Minerals reported to co-occur with stefanweissite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,REE)₂Zr₂(Nb,Ti)(Ti,Nb)₂FeO₁₄
- Mohs hardness
- 4.5
- Density
- 5.254 g/cm³
- Colors
- Streak
- Light brown to yellow
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Flattened prismatic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- hydrothermal veins in shales
Where rockhounds find stefanweissite
Classic worldwide localities
- In den Dellen (Zieglowski) pumice quarry, Rhineland-Palatinate, Germany
Field-hunting tip
Where it forms: hydrothermal veins in shales. If you start seeing vauxite, paravauxite, wardite in float, you are in the right ground. Typical habit: flattened prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find stefanweissite on the map
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