Celadonite - Encyclopedia

    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


This service is used to secure web forms of our website and required if you want to contact us. By accepting it you agree to Google's privacy policy: https://policies.google.com/privacy

Google Analytics

Google Analytics is a service used on our website that tracks, reports traffic and measures how users interact with our website content in order for us to improve it and provide better services.


Our website allows you to like or share its content on Facebook social network. By activating and using it you agree to Facebook's privacy policy: https://www.facebook.com/policy/cookies/


Integrated videos provided by YouTube are used on our website. By accepting to watch them you agree to Google's privacy policy: https://policies.google.com/privacy


Integrated tweets and share services of Twitter are used on our website. By accepting and using these you agree to Twitter's privacy policy: https://help.twitter.com/en/rules-and-policies/twitter-cookies


Our website allows you to share its content on PInterest social network. By activating and using it you agree to PInterest's privacy policy: https://policy.pinterest.com/en/privacy-policy/