Uranosilite is a rare uranyl silicate mineral known for its distinct acicular or needle-like crystal habit often forming radiating sprays. Due to its radioactive nature and scarcity, it is highly sought after by advanced mineral collectors specializing in uranium secondary minerals.
Is this uranosilite?
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 uranosilite with a known reference. Uranosilite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellowish white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular.
Often confused with
Uranosilite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Kasolite is the harder of the two (Mohs 4-5 vs. 3); streak differs, so Uranosilite leaves white, Kasolite leaves pale yellow-brown; luster reads vitreous on Uranosilite and subadamantine to greasy, dull to earthy when massive on Kasolite.
How to tell apart: Streak differs, so Uranosilite leaves white, Uranophane leaves yellowish white.
Often found alongside uranosilite
Minerals reported to co-occur with uranosilite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (UO₂)Si₇O₁₅
- Mohs hardness
- 3
- Density
- 3.25 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular
- Cleavage
- None
- Fluorescence
- Bright green under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a uranium deposit
Where rockhounds find uranosilite
Classic worldwide localities
- Menzenschwand, Black Forest, Germany
Field-hunting tip
Where it forms: In a uranium deposit. If you start seeing studtite, uranophane, quartz in float, you are in the right ground. Typical habit: acicular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify uranosilite?+
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Is uranosilite safe to handle?+
What rocks look like uranosilite?+
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Find uranosilite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
