Orthowalpurgite is an extremely rare secondary bismuth arsenate mineral found in the oxidation zones of uranium-bismuth deposits. It typically occurs as minute, thin tabular crystals or radial clusters that are easily mistaken for the triclinic mineral walpurgite. Collectors primarily find this species as micro-specimens associated with other rare bismuth minerals.
Is this orthowalpurgite?
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 orthowalpurgite with a known reference. Orthowalpurgite 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: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: crystalline, tabular.
Often confused with
Orthowalpurgite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Orthowalpurgite is noticeably harder (Mohs 4.5 vs. 3.5).
How to tell apart: Luster reads adamantine on Orthowalpurgite and vitreous, silky in aggregates on Mixite.
How to tell apart: Streak differs, so Orthowalpurgite leaves pale yellow, Atelestite leaves white; luster reads adamantine on Orthowalpurgite and resinous to adamantine on Atelestite.
Often found alongside orthowalpurgite
Minerals reported to co-occur with orthowalpurgite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (UO₂)Bi₄O₄(AsO₄)₂·2H₂O
- Mohs hardness
- 4.5
- Density
- 6.5 g/cm³
- Colors
- Streak
- Pale yellow
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Crystalline, tabular
- Cleavage
- Indistinct on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare mineral, probably formed by weathering of an earlier bismuth-bearing sulfide
Where rockhounds find orthowalpurgite
Classic worldwide localities
- The Schmiedestollen, Wittichen, Black Forest, Germany (type locality)
Field-hunting tip
Where it forms: A very rare mineral, probably formed by weathering of an earlier bismuth-bearing sulfide. If you start seeing preisingerite, anatase, quartz in float, you are in the right ground. Typical habit: crystalline, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify orthowalpurgite?+
Where is orthowalpurgite found?+
Is orthowalpurgite safe to handle?+
What rocks look like orthowalpurgite?+
What minerals are found with orthowalpurgite?+
What kind of rock does orthowalpurgite form in?+
What is orthowalpurgite used for?+
Find orthowalpurgite on the map
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