Gummite - Encyclopedia

    Class : -
    Subclass : -
    Crystal system : -
    Chemistry : -
    Rarity : Quite common


Like garnierite or bauxite, gummite is not a mineral but a collection of minerals. The term gummite in fact designates secondary cryptocrystalline uranium minerals, generally powdery, formed in a hot or temperate climate by oxidation of uraninite (often in its concretionary pitchblende facies). It was named thus in allusion to its resin or gum appearance. These are essentially oxides and silicates of uranium associated with various metals. Almost all gummites retain the characteristic structures of uraninites and especially pitchblendes which they epigenize. The yellow gummites, the most common, are largely composed of uranotile (or uranophane), the orange gummites (sometimes red) of curite, billiétite or ianthinite. Black gummites correspond to altered rocks colored black by small quantities of residual UO2, surviving the transformation into UO3 during the oxidation of pitchblende. Gummites constitute a significant part of the uranium ore in the oxidation zones of the deposits.

Main photo : Gummite from Luiswishi Mine, Kawama, Haut-Katanga, DR Congo © Paul de Bondt

Gummite in the World

Gummite is present in many deposits around the world. The most beautiful masses certainly come from the uranium deposits of Katanga (Democratic Republic of Congo), but also from the United States such as Grafton (New Hampshire) or San Rafael Swell Mining District (Utah), and also from Pribram (Czech Republic).

Gummite in France

In France, gummite is reported in beautiful samples in Chaméane (Puy-de-Dôme), in Saint-Priest-la-Prugne (Loire), in Margnac (Haute-Vienne), and in numerous other localities.

Right photo : Gummite from Chaméane, Puy-de-Dôme, France © Pascal Chollet

Fakes and treatments

No fakes recorded for this mineral species.



Hardness : 2.5 to 5
Density : 3.9 to 6.4
Fracture : Irregular to conchoidal
Streak : Yellow, brown, green


TP : Translucent to opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None


Solubility : -

Magnetism : NoneRadioactivity : Very strong

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