Threadgoldite is a rare uranyl phosphate mineral characterized by its bright yellow, thin platy crystals that resemble mica. It is primarily found as a secondary mineral in the oxidized zones of uranium deposits and requires careful handling due to its radioactivity.
Is this threadgoldite?
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 threadgoldite with a known reference. Threadgoldite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Threadgoldite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Threadgoldite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: yellow, golden yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: thin platy crystals, micaceous aggregates.
Often confused with
Threadgoldite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Threadgoldite leaves yellow, Autunite leaves pale yellow.
How to tell apart: Streak differs — Threadgoldite leaves yellow, Torbernite leaves pale green; luster reads pearly on Threadgoldite and vitreous on Torbernite.
Often found alongside threadgoldite
Minerals reported to co-occur with threadgoldite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al(UO₂)₂(PO₄)₂(OH)·8H₂O
- Mohs hardness
- 2
- Density
- 3.9 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Thin Platy Crystals, Micaceous Aggregates
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Uranium-bearing Hydrothermal Deposits
- Typical price
- $50-300 per specimen depending on size and crystal quality
Where rockhounds find threadgoldite
Classic worldwide localities
- Musonoi Mine, Democratic Republic of the Congo
- Shinkolobwe Mine, Democratic Republic of the Congo
Field-hunting tip
Look in oxidized zones of uranium-bearing hydrothermal deposits country — that is the host setting where threadgoldite typically forms. If you start seeing meta-autunite, parsonsite, renardite in float, you are in the right ground. Field specimens usually show a thin platy crystals, micaceous aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify threadgoldite?+
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How much is threadgoldite worth?+
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Find threadgoldite on the map
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