Guilleminite
A variety of Minerals

What is Guilleminite?
Guilleminite (Ba(UO2)3(SeO3)2(OH)4•3H2O) is a uranium mineral named by R. Pierrot, J. Toussaint, and T. Verbeek in 1965 in honor of Jean Claude Guillemin (1923–1994), a chemist and mineralogist. It is a rare uranium/selenium mineral found at the Musonoi Mine in the Katanga Province of the Democratic Republic of the Congo. This secondary mineral also includes barium in its structure, in addition to selenium and uranium. It is bright yellow in colour and usually has an acicular crystal habit. It has a Mohs hardness of 2–3.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Guilleminite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Guilleminite Localities Map
See where Guilleminite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Quick Facts
Physical Properties
- Color
- Bright yellow
- Hardness (Mohs)
- 2
- Density
- 5.08 g/cm³
- Streak
- Light yellow
Chemical Properties
- Chemical Formula
- Ba(UO2)3(SeO3)2O2 · 3H2O
- Elements
- Ba, H, O, Se, U

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Guilleminite FAQs
How do I identify Guilleminite?
Guilleminite can be identified by its hardness of 2 on the Mohs scale, Bright yellow color. Look for these key characteristics when examining specimens.
What color is Guilleminite?
Guilleminite typically appears in Bright yellow. Color can vary depending on impurities and formation conditions.
How hard is Guilleminite?
Guilleminite has a hardness of 2 on the Mohs scale. This makes it a soft mineral that can be scratched easily.


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