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 — Ningyoite leaves white, Autunite leaves pale yellow; luster reads dull on Ningyoite and pearly on Autunite.
How to tell apart: Streak differs — 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 — 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 — that is 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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