Ningyoite is a rare secondary uranium phosphate mineral usually found as fine-grained, earthy coatings or aggregates within sedimentary sandstone deposits. It is notable for its occurrence in the Ningyo-toge mine and requires careful handling due to its natural radioactivity.
Is this ningyoite?
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 ningyoite with a known reference. Ningyoite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ningyoite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ningyoite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: brown, yellowish-brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: microcrystalline aggregates, earthy.
Often confused with
Ningyoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ningyoite leaves white, Autunite leaves pale yellow; luster reads dull on Ningyoite and pearly on Autunite.
How to tell apart: Streak differs, so Ningyoite leaves white, Torbernite leaves pale green; luster reads dull on Ningyoite and vitreous on Torbernite.
How to tell apart: Coffinite is the harder of the two (Mohs 5 vs. 3); streak differs, so Ningyoite leaves white, Coffinite leaves brownish-black.
Often found alongside ningyoite
Minerals reported to co-occur with ningyoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- U₁₋ₓCaₓ(PO₄)₂·1-2H₂O
- Mohs hardness
- 3
- Density
- 4.45 g/cm³
- Colors
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Microcrystalline Aggregates, Earthy
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Deposits in Sandstone
- Typical price
- $50-300 per specimen
Where rockhounds find ningyoite
Classic worldwide localities
- Ningyo-toge mine, Japan
- Wyoming, USA
- Kazakhstan
Field-hunting tip
Look in sedimentary deposits in sandstone country, the host setting where ningyoite typically forms. If you start seeing uraninite, coffinite, quartz in float, you are in the right ground. Field specimens usually show a microcrystalline aggregates, earthy habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ningyoite on the map
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