BOLTWOODITE

    Class : Silicates
    Subclass : Nesosilicates
    Crystal System : Monoclinic
    Chemistry : (H3O)K(UO2)SiO4
    Rarity : Rare

Boltwoodite is a complex uranium-potassium silicate, one of many secondary uranium minerals that form by surface weathering of pitchblende and uraninite. It was named in honor of Bertram Borden Boltwood, a radiochemist at Yale University and a pioneer in rock dating using the U/Pb method. Boltwoodite crystals are acicular or fibrous, small (less than 1 cm), and usually occur in radiating yellow aggregates. It is a highly radioactive mineral (over 66% UO3).

Main photo : Boltwoodite from Goanikontes, Erongo, Namibia © Elise Chaigneau

Boltwoodite from Goanikontes, Erongo, Namibia © Jean-Pierre Barral
Boltwoodite from Goanikontes, Erongo, Namibia © Jean-Pierre Barral
Boltwoodite from Goanikontes, Erongo, Namibia © Stephan Wolfsried
Boltwoodite and fluorite from New Method Mine, California, USA © Jason B. Smith

Boltwoodite in the World

Although rare, boltwoodite occurs in deposits from different geological contexts. The finest specimens, radiated aggregates of 2 cm, come from Rössing and Goanikontes (Namibia) where boltwoodite is exceptionally abundant. Boltwoodite is also quite common in uranium deposits in Colorado and California.

Boltwoodite in France

In France, boltwoodite is reported at the Bernardan mine near Meilhac (Haute-Vienne).

Twinning and special crystallizations

No twin known for this mineral species.

Fakes and treatments

No fake identify for this mineral species.


Hardness : 3.5 to 4
Density : 4.7
Fracture : Irregular
Trace : Yellow

TP : Translucent
RI : 1.668 to 1.703
Birefringence : 0.007 to 0.008
Optical character : Biaxial +
Pleochroism : Low
Fluorescence : Green

Solubility : -

Magnetism : None
Radioactivity : Very strong

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