Packratite is a rare secondary uranium mineral typically found as efflorescences or crusts in arid cave environments where packrat middens are present. It is highly sought after by collectors for its brilliant fluorescent response under ultraviolet light, though it requires careful handling due to its radioactivity and toxicity.
Is this packratite?
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 packratite with a known reference. Packratite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Packratite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Packratite typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange, brown, reddish-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crusts, aggregates, efflorescences.
Often confused with
Packratite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Packratite leaves yellow, Autunite leaves pale yellow; luster reads resinous on Packratite and pearly on Autunite.
How to tell apart: Streak differs — Packratite leaves yellow, Torbernite leaves pale green; luster reads resinous on Packratite and vitreous on Torbernite.
How to tell apart: Luster reads resinous on Packratite and pearly on Meta-autunite.
Often found alongside packratite
Minerals reported to co-occur with packratite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂(UO₂)₂(AsO₄)₂·10H₂O
- Mohs hardness
- 2.5
- Density
- 2.65 g/cm³
- Streak
- Yellow
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Crusts, Aggregates, Efflorescences
- Cleavage
- None
- Fluorescence
- Bright Yellow Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Uranium-vanadium Deposits in Sandstone
- Typical price
- $20-150 per specimen depending on matrix
Where rockhounds find packratite
Classic worldwide localities
- San Juan County, Utah, USA
- Grand County, Utah, USA
- Montrose County, Colorado, USA
Field-hunting tip
Look in sedimentary uranium-vanadium deposits in sandstone country — that is the host setting where packratite typically forms. If you start seeing uraninite, tyuyamunite, gypsum in float, you are in the right ground. Field specimens usually show a crusts, aggregates, efflorescences habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify packratite?+
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Find packratite on the map
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