Formula: KMgFe3+Si4O10(OH)2
Phyllosilicate (sheet silicate), mica group, forms a series with muscovite
Specific gravity: 2.95 to 3.05
Hardness: 2
Streak: Greenish white
Colour: Blue-green, olive green, apple green
Solubility: Decomposed by hydrochloric acid
Common impurities: Mn,Ca,Na

Metamorphic environments
Basaltic cavities

Celadonite occurs as vesicle lining and coatings in altered volcanic rocks of intermediate to basic compositions, under low grade metamorphism (Webmin, HOM), and as amygdule fillings in basalt or granite andesite (HOM). Celadonite formed in vesicular basalt derives its essential magnesium, iron, and silica from olivine, and its other constituents from deuteric solutions; it is most abundant in these cavities, but it also replaces olivine, and less commonly enstatite-ferrosilite or ground mass material (AM 26.683-708).
Celadonite occurs throughout the zeolite and prehnite-pumpellyite facies but does not occur in the greenschist facies (AM 49.1031-1083).
Associated minerals include montmorillonite, clinoptilolite, heulandite, laumontite, prehnite, chlorite, chalcedony, quartz and calcite (HOM, Dana).


There are three co-type localities, Planitz, Zwickau, Saxony, Germany, and Malga Canalece-San Valentino, Brentonico, and Tierno-Besagno, Mori, both at Mt. Baldo, Trento Province, Trentino-Alto Adige, Italy.

At the Merehead Quarry, Cranmore, Mendip, Somerset, England, UK, a specimen has been found consisting of crystalline goethite, calcite and bands of orange-brown iron oxides, with a single discontinuous band of celadonite (JRS 13.14).

At the Cripple Creek mining district, Colorado, USA, celadonite has been reported in vesicles and cracks in volcanic breccia and altered tephritic-phonolite (phonolite with felsics comprising 60-90% feldspathoids and alkali feldspar/total feldspar 0.9-0.5) (Minrec 36.2.167).

At Reno, Nevada, USA, celadonite occurs as vesicular fillings in a fine-grained olivine basalt. Most of the cavities are completely filled with celadonite, but a few are hollow or contain irregular areas of iron-rich saponite, and a few of the smallest cavities contain only saponite (AM 26.683-708).

At Sandoval county, New Mexico, USA, celadonite fills irregular or flattened vesicular cavities up to 10 mm in size. Some of the vesicles contain only celadonite, but others contain associated calcite and saponite (AM 26.683-708).

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