Metakahlerite is a rare secondary uranium mineral that forms through the dehydration of primary minerals in oxidized hydrothermal veins. Collectors prize its bright yellow tabular crystals, which are strongly fluorescent under UV light. Due to its radioactive and toxic nature, it should only be handled by experienced mineral collectors with proper safety protocols.
Is this metakahlerite?
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 metakahlerite with a known reference. Metakahlerite 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 yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly on {001}.
- 4Match the color rangeCompare against the expected color range: sulfur yellow.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals, micaceous aggregates.
Often confused with
Metakahlerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Metakahlerite leaves light yellow, Autunite leaves pale yellow; luster reads pearly on {001} on Metakahlerite and vitreous, pearly on {001} on Autunite.
How to tell apart: Streak differs, so Metakahlerite leaves light yellow, Meta-autunite leaves yellow.
How to tell apart: Streak differs, so Metakahlerite leaves light yellow, Torbernite leaves pale green; luster reads pearly on {001} on Metakahlerite and vitreous, subadamantine, waxy, pearly on cleavages; becoming dull on dehydration to metatorbernite on Torbernite.
Often found alongside metakahlerite
Minerals reported to co-occur with metakahlerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe(UO₂)₂(AsO₄)₂·8H₂O
- Mohs hardness
- 2.5
- Density
- 3.73-3.77 g/cm³
- Colors
- Sulfur yellow
- Streak
- Light yellow
- Luster
- Pearly on {001}
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular crystals, micaceous aggregates
- Cleavage
- Perfect on {001}; good on {010}
- Fluorescence
- Bright green under UV light
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in the oxidized zone of U–As bearing deposits
Where rockhounds find metakahlerite
Classic worldwide localities
- Black Forest, from the Sophia and St. Joseph mines and at the Schmiedestollen, near Wittichen, and from Menzenschwand, Germany
- Ellweiler, Rhineland-Palatinate, Germany
- Schneeberg, Saxony, Germany
- Hüttenberg, Carinthia, Austria
- Southwick Cliffs, near Dalbeattie, Kirkcudbrightshire, Scotland
- Krantzberg mine, 20 km west of Karibib, Namibia
Field-hunting tip
Where it forms: A secondary mineral in the oxidized zone of U–As bearing deposits. If you start seeing arseniosiderite, scorodite, löllingite in float, you are in the right ground. Typical habit: tabular crystals, micaceous aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify metakahlerite?+
Where is metakahlerite found?+
Is metakahlerite safe to handle?+
What rocks look like metakahlerite?+
What minerals are found with metakahlerite?+
What kind of rock does metakahlerite form in?+
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Find metakahlerite on the map
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