Soddyite is a striking secondary uranium mineral characterized by its bright yellow to yellow-orange crystal clusters. It is typically found in the oxidized zones of uranium deposits and is highly prized by collectors for its vibrant fluorescence under ultraviolet light.
Is this soddyite?
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 soddyite with a known reference. Soddyite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to adamantine, dull when earthy.
- 4Match the color rangeCompare against the expected color range: yellow, canary yellow, yellowish green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic, pyramidal, striated.
Often confused with
Soddyite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous to adamantine, dull when earthy on Soddyite and subadamantine to greasy, dull to earthy when massive on Kasolite.
How to tell apart: Soddyite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs, so Soddyite leaves pale yellow, Uranophane leaves yellowish white.
Often found alongside soddyite
Minerals reported to co-occur with soddyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (UO₂)₂SiO₄·2H₂O
- Mohs hardness
- 3.5
- Density
- 4.63-4.70 g/cm³
- Streak
- Pale yellow
- Luster
- Vitreous to adamantine, dull when earthy
- Transparency
- Translucent to transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic, pyramidal, striated
- Cleavage
- Perfect on {001}, good on {111}
- Fluorescence
- Weak orange yellow under SW and LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed by oxidation of uraninite
Where rockhounds find soddyite
Classic worldwide localities
- Ruggles pegmatite, Grafton, Grafton Co., New Hampshire, USA
- Steel City mine, Yavapai Co., Arizona, USA
- Jackpile mine, Laguna, Valencia Co., New Mexico, USA
- Lucky Mc mine, Fremont Co., Wyoming, USA
- Kasolo, Swambo, and in the Musonoi mine, Kolwezi, Katanga Province, Congo (Shaba Province, Zaire)
- Norrabees pegmatite, Namaqualand, Cape Province, South Africa
Field-hunting tip
Where it forms: A secondary mineral formed by oxidation of uraninite. If you start seeing kasolite, sklodowskite, uranophane in float, you are in the right ground. Typical habit: prismatic, pyramidal, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify soddyite?+
Where is soddyite found?+
Is soddyite safe to handle?+
What rocks look like soddyite?+
What minerals are found with soddyite?+
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Find soddyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
