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, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish blue.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: very dark greenish blue.
- 5Look at form & habitCrystal system: triclinic. 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, so Packratite leaves grayish blue, Autunite leaves pale yellow.
How to tell apart: Streak differs, so Packratite leaves grayish blue, Torbernite leaves pale green.
How to tell apart: Streak differs, so Packratite leaves grayish blue, Meta-autunite leaves yellow; luster reads vitreous on Packratite and pearly to dull 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
- Ca₁₁(AsV₁₀V₂As₆O₅₁)₂·83H₂O
- Mohs hardness
- ~2
- Density
- 2.36 g/cm³
- Colors
- Very dark greenish blue
- Streak
- Grayish blue
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Crusts, aggregates, efflorescences
- Cleavage
- Fair on {001}, {110} and {11̄0}
- Fluorescence
- Bright yellow under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed by the oxidation of montroseite-corvusite assemblages in a moist environment
Where rockhounds find packratite
Classic worldwide localities
- Packrat mine, Gateway district, Mesa County, Colorado, USA
Field-hunting tip
Where it forms: A secondary mineral formed by the oxidation of montroseite-corvusite assemblages in a moist environment. If you start seeing gatewayite, morrisonite, vanarsite in float, you are in the right ground. Typical habit: crusts, aggregates, efflorescences. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify packratite?+
Where is packratite found?+
Is packratite safe to handle?+
What rocks look like packratite?+
What minerals are found with packratite?+
What kind of rock does packratite form in?+
What is packratite used for?+
Find packratite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
