Phosphuranylite is a rare secondary uranium phosphate that typically forms as vibrant yellow earthy crusts or thin coatings on other uranium minerals. Collectors should look for its strong yellow-green fluorescence under UV light, which is a key diagnostic feature. It is strictly for advanced collectors who are equipped to handle radioactive materials safely.
Is this phosphuranylite?
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 phosphuranylite with a known reference. Phosphuranylite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Phosphuranylite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Phosphuranylite typically shows a earthy luster.
- 4Match the color rangeCompare against the expected color range: yellow, golden yellow, orange-yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, earthy masses, coatings, crusts.
Often confused with
Phosphuranylite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Phosphuranylite leaves yellow, Autunite leaves pale yellow; luster reads earthy on Phosphuranylite and pearly on Autunite.
How to tell apart: Streak differs — Phosphuranylite leaves yellow, Torbernite leaves pale green; luster reads earthy on Phosphuranylite and vitreous on Torbernite.
How to tell apart: Curite is the harder of the two (Mohs 4-5 vs. 2-3); streak differs — Phosphuranylite leaves yellow, Curite leaves orange; luster reads earthy on Phosphuranylite and adamantine on Curite.
Often found alongside phosphuranylite
Minerals reported to co-occur with phosphuranylite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KCa(H₃O)₃(UO₂)₇(PO₄)₄O₄·8H₂O
- Mohs hardness
- 2-3
- Density
- 4.1-4.3 g/cm³
- Streak
- Yellow
- Luster
- Earthy
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Earthy Masses, Coatings, Crusts
- Cleavage
- Perfect On {010}
- Fluorescence
- Strong Yellow-green Under SW and LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Uranium-bearing Pegmatites and Hydrothermal Deposits
- Typical price
- $20-150 for micro-mounts and small specimens
Where rockhounds find phosphuranylite
Classic worldwide localities
- Kobokobo, Democratic Republic of the Congo
- Ruggles Mine, New Hampshire, USA
- Wölsendorf, Bavaria, Germany
- Asselborn, Luxembourg
Field-hunting tip
Look in oxidized zones of uranium-bearing pegmatites and hydrothermal deposits country — that is the host setting where phosphuranylite typically forms. If you start seeing autunite, torbernite, curite in float, you are in the right ground. Field specimens usually show a platy crystals, earthy masses, coatings, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find phosphuranylite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
