Phurcalite is a rare secondary uranium phosphate mineral that typically forms as striking, bright yellow, radiating clusters of needle-like or platy crystals. It is highly prized by collectors for its intense green-yellow fluorescence under ultraviolet light and is most commonly found in the weathered zones of uranium-rich hydrothermal veins.
Is this phurcalite?
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 phurcalite with a known reference. Phurcalite sits at Mohs 2.5-3, 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, may be silky in aggregates.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular or radiating clusters of platy crystals.
Often confused with
Phurcalite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside phurcalite
Minerals reported to co-occur with phurcalite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂(H₂O)₆[(UO₂)₃O₂(PO₄)₂]·H₂O
- Mohs hardness
- 2.5-3
- Density
- 4.22 g/cm³
- Colors
- Streak
- Pale yellow
- Luster
- Vitreous to adamantine, may be silky in aggregates
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular or radiating clusters of platy crystals
- Cleavage
- {010}, {001}, perfect to good; {100}, good
- Fluorescence
- Bright yellow-green under UV light
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in cracks and fractures in granite and granite pegmatites
Where rockhounds find phurcalite
Classic worldwide localities
- Ram claims, Pinto Mountains, Riverside Co., and at the Shale Hills, near Taft, Kern Co., California, USA
- Posey mine, Red Canyon, San Juan Co., and in the La Sal Mountains, Grand Co., Utah, USA
- Bergen, Saxony
- Wittichen, Black Forest
- Waidhaus, Bavaria
- Merrivale quarry, Dartmoor, Devon, England
Field-hunting tip
Where it forms: A secondary mineral in cracks and fractures in granite and granite pegmatites. If you start seeing autunite, meta-autunite, uranophane in float, you are in the right ground. Typical habit: acicular or radiating clusters of platy crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify phurcalite?+
Where is phurcalite found?+
Is phurcalite safe to handle?+
What rocks look like phurcalite?+
What minerals are found with phurcalite?+
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What is phurcalite used for?+
Find phurcalite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
