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 3-4, 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: greasy.
- 4Match the color rangeCompare against the expected color range: brown, brownish green.
- 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 greasy on Ningyoite and vitreous, pearly on {001} on Autunite.
How to tell apart: Streak differs, so Ningyoite leaves white, Torbernite leaves pale green; luster reads greasy on Ningyoite and vitreous, subadamantine, waxy, pearly on cleavages; becoming dull on dehydration to metatorbernite on Torbernite.
How to tell apart: Coffinite is the harder of the two (Mohs 5-6 vs. 3-4); streak differs, so Ningyoite leaves white, Coffinite leaves grayish black; luster reads greasy on Ningyoite and dull to adamantine on Coffinite.
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
- (U,Ca,Ce)₂(PO₄)₂·1-2H₂O
- Mohs hardness
- 3-4
- Density
- 4.75 g/cm³
- Colors
- Streak
- White
- Luster
- Greasy
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Microcrystalline aggregates, earthy
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- The principal uranium mineral, as coatings and filling cavities in carbonaceous conglomerate (Ningyo mine, Japan); in uranium deposits in organic-rich conglomerate-sandstone-mudstone (British Columbia, Canada)
Where rockhounds find ningyoite
Classic worldwide localities
- Ningyo-Toge uranium mine, Tottori Prefecture, Japan
- Tyee and Blizzard uranium deposits, 60 and 30 km southeast of Kelowna, Okanagan district, British Columbia, Canada
- Dzhantuar and Rudnoye uranium deposits, Auminzatau Mountains, central Kyzylkum region, Uzbekistan
Field-hunting tip
Where it forms: The principal uranium mineral, as coatings and filling cavities in carbonaceous conglomerate (Ningyo mine, Japan); in uranium deposits in organic-rich conglomerate-sandstone-mudstone (British Columbia, Canada). If you start seeing pyrite, marcasite, sphalerite in float, you are in the right ground. Typical habit: microcrystalline aggregates, earthy. 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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