Schmitterite is an extremely rare uranium tellurite mineral typically found as a secondary oxidation product. It usually appears as fine-grained, pale yellow crusts or tiny, delicate platy crystals, often associated with other rare tellurium minerals in uranium-rich localities.
Is this schmitterite?
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 schmitterite with a known reference. Schmitterite sits at Mohs ~1, 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.
- 4Match the color rangeCompare against the expected color range: colorless, light yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, crusts, pulverulent aggregates.
Often confused with
Schmitterite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Carnotite is the harder of the two (Mohs 2 vs. ~1); streak differs, so Schmitterite leaves white, Carnotite leaves strontian-yellow; luster reads pearly on Schmitterite and dull, earthy; silky when crystalline on Carnotite.
How to tell apart: Autunite is the harder of the two (Mohs 2-2.5 vs. ~1); streak differs, so Schmitterite leaves white, Autunite leaves pale yellow; luster reads pearly on Schmitterite and vitreous, pearly on {001} on Autunite.
Often found alongside schmitterite
Minerals reported to co-occur with schmitterite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- UO₂TeO₃
- Mohs hardness
- ~1
- Density
- 6.878 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy crystals, crusts, pulverulent aggregates
- Cleavage
- On {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the oxidized zone of a hydrothermal Au–Te deposit (Moctezuma mine, Mexico); in the oxidized zone of a uranium deposit (Shinkolobwe, Congo)
Where rockhounds find schmitterite
Classic worldwide localities
- Moctezuma (Bambolla) mine, 12 km south of Moctezuma, and at the San Miguel prospect, 10 km northwest of the Moctezuma mine, Sonora, Mexico
- Shinkolobwe, Katanga Province, Congo (Shaba Province, Zaire)
Field-hunting tip
Where it forms: In the oxidized zone of a hydrothermal Au–Te deposit (Moctezuma mine, Mexico); in the oxidized zone of a uranium deposit (Shinkolobwe, Congo). If you start seeing emmonsite, mackayite, cuzticite in float, you are in the right ground. Typical habit: platy crystals, crusts, pulverulent aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify schmitterite?+
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Is schmitterite safe to handle?+
What rocks look like schmitterite?+
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Find schmitterite on the map
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