Metakirchheimerite is a rare secondary uranium mineral often forming delicate, pink tabular crystals or crusts. Collectors primarily look for it in oxidized zones of cobalt-bearing uranium deposits, where it is often associated with other fluorescent minerals.
Is this metakirchheimerite?
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 metakirchheimerite with a known reference. Metakirchheimerite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly on {001}.
- 4Match the color rangeCompare against the expected color range: light pink.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals, micaceous crusts.
Often confused with
Metakirchheimerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Metakirchheimerite leaves white, Autunite leaves pale yellow; luster reads pearly on {001} on Metakirchheimerite and vitreous, pearly on {001} on Autunite.
How to tell apart: Streak differs, so Metakirchheimerite leaves white, Meta-autunite leaves yellow.
How to tell apart: Streak differs, so Metakirchheimerite leaves white, Torbernite leaves pale green; luster reads pearly on {001} on Metakirchheimerite and vitreous, subadamantine, waxy, pearly on cleavages; becoming dull on dehydration to metatorbernite on Torbernite.
Often found alongside metakirchheimerite
Minerals reported to co-occur with metakirchheimerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Co(UO₂)₂(AsO₄)₂(H₂O)₅·3H₂O
- Mohs hardness
- 2-2.5
- Density
- 3.2-3.25 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly on {001}
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular crystals, micaceous crusts
- Cleavage
- Perfect on {001}; good on {010}
- Fluorescence
- Bright yellow-green under UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare secondary mineral formed in the oxidized zone of a U–As deposit
Where rockhounds find metakirchheimerite
Classic worldwide localities
- Dump of the Sophia mine, near Wittichen, Black Forest, Germany (type locality)
Field-hunting tip
Where it forms: A very rare secondary mineral formed in the oxidized zone of a U–As deposit. If you start seeing metakahlerite, nováčekite, metaheinrichite in float, you are in the right ground. Typical habit: tabular crystals, micaceous crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find metakirchheimerite on the map
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