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, so 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, so 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, 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
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Find haiweeite on the map
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