CELADONITE

    Class : Silicates
    Subclass : Phyllosilicates
    Crystal system : Monoclinic
    Chemistry : K(Mg,Fe)2Si4O10(OH)2
    Rarity : Quite common

Celadonite is a micas group mineral that crystallizes in altered volcanic rocks of basic to intermediate composition, where it replaces ferromagnesian silicates. It reflects light metamorphism (zeolite facies), or the action of late hydrothermal solutions and then fills the cavities of the andesites and basalts. It is notably associated with montmorillonite, prehnite and zeolites. Its name comes from the French “céladon” which designates a pale green color like that of the mineral. It forms tiny micaceous-looking lamellae, and earthy aggregates usually pale olive green to bluish green in color.

Main photo : Celadonite from Terra do Baptista, Madeira, Portugal © Pedro Alves

Celadonite in the World

Occurrences are numerous, notably in Japan, the Faroe Islands and Iceland (in hydrothermal alteration of baslates), and in the United States. The samples, however, are never spectacular and offer little museological interest.

Celadonite in France

In France, cecidonite is reported from the basalt quarry of St-Jean-des-Ollières (Puy-de-Dôme) but also in French Polynesia, New Caledonia and the Kerguelen Islands.

Twinning and special crystallizations

No known twin.

Fakes and treatments

No fake identified for this mineral species.


Hardness : 2
Density : 2.95 to 3.05
Fracture : Micaceous
Streak : White

TP : Translucent to transparent
RI : 1.606 to 1.662
Birefringence : 0.027
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrochloric acid


Magnetism : None
Radioactivity : None

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