Haiweeite is a rare calcium uranyl silicate that typically forms as delicate, radiating, fan-shaped clusters or soft, powdery coatings. It is highly sought after by collectors for its brilliant neon-green fluorescence under short-wave ultraviolet light, although it requires cautious handling due to its radioactive nature.
Is this haiweeite?
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 haiweeite with a known reference. Haiweeite sits at Mohs 1 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Haiweeite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Haiweeite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: yellow, pale yellow, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: radiating aggregates, spherulitic, crusts.
Often confused with
Haiweeite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Uranophane is the harder of the two (Mohs 2.5 vs. 1); streak differs — Haiweeite leaves white, Uranophane leaves pale yellow; luster reads pearly on Haiweeite and vitreous on Uranophane.
How to tell apart: Autunite is the harder of the two (Mohs 2-2.5 vs. 1); streak differs — Haiweeite leaves white, Autunite leaves pale yellow.
Often found alongside haiweeite
Minerals reported to co-occur with haiweeite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca(UO₂)₂(Si₂O₅)₃·5H₂O
- Mohs hardness
- 1
- Density
- 2.8 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Radiating Aggregates, Spherulitic, Crusts
- Cleavage
- Perfect
- Fluorescence
- Bright Green Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins, Sedimentary Uranium Deposits
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find haiweeite
Classic worldwide localities
- Haiwee Reservoir, California, USA
- Grand Canyon, Arizona, USA
- Schneeberg, Germany
- Lodève, France
Field-hunting tip
Look in hydrothermal veins, sedimentary uranium deposits country — that is the host setting where haiweeite typically forms. If you start seeing uraninite, gypsum, calcite in float, you are in the right ground. Field specimens usually show a radiating aggregates, spherulitic, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify haiweeite?+
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Find haiweeite on the map
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