Kasolite is a striking radioactive secondary uranium mineral often found as small, vibrant yellow acicular crystals or earthy crusts. It is most frequently collected by specialist radioactive mineral enthusiasts and is typically found in the oxidized zones of uranium ore bodies where it forms as an alteration product of uraninite.
Is this kasolite?
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 kasolite with a known reference. Kasolite sits at Mohs 4-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellow-brown.
- 3Read the lusterHold the specimen under a strong light. Luster: subadamantine to greasy, dull to earthy when massive.
- 4Match the color rangeCompare against the expected color range: yellow, green, gray green, yellow brown, reddish orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, prismatic, radial.
Often confused with
Kasolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Kasolite leaves pale yellow-brown, Curite leaves orange; luster reads subadamantine to greasy, dull to earthy when massive on Kasolite and adamantine on Curite.
How to tell apart: Streak differs, so Kasolite leaves pale yellow-brown, Fourmarierite leaves orange; luster reads subadamantine to greasy, dull to earthy when massive on Kasolite and adamantine to subadamantine on Fourmarierite.
How to tell apart: Kasolite is noticeably harder (Mohs 4-5 vs. 2.5); streak differs, so Kasolite leaves pale yellow-brown, Becquerelite leaves yellow; luster reads subadamantine to greasy, dull to earthy when massive on Kasolite and adamantine to greasy on Becquerelite.
Often found alongside kasolite
Minerals reported to co-occur with kasolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb(UO₂)(SiO₄)·H₂O
- Mohs hardness
- 4-5
- Density
- 5.83-6.5 g/cm³
- Streak
- Pale yellow-brown
- Luster
- Subadamantine to greasy, dull to earthy when massive
- Transparency
- Transparent to translucent, opaque
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, prismatic, radial
- Cleavage
- Perfect on {001}, indistinct on {100} and {010}
- Fluorescence
- Bright yellow-green under UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An oxidization product of uraninite
Where rockhounds find kasolite
Classic worldwide localities
- Ruggles pegmatite, near Grafton, Grafton Co., New Hampshire, USA
- Green Monster mine, Goodsprings district, Clark Co., and the 4-D mine, Marietta district, Mineral Co., Nevada, USA
- Ross-Adams mine, Bokan Mountain, Prince of Wales Island, Alaska, USA
- Shinkolobwe, and the Musonoi mine, Kolwezi, Katanga Province, Congo (Shaba Province, Zaire)
- Mounana, Gabon
- Wölsendorf, Bavaria, Germany
Field-hunting tip
Where it forms: An oxidization product of uraninite. If you start seeing uraninite, torbernite, curite in float, you are in the right ground. Typical habit: fibrous, prismatic, radial. Train your eye for that shape before scanning the outcrop.
More kasolite photos
Common questions
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Find kasolite on the map
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