Celadonite: Properties and Occurrences

Celadonite is a mica group mineral, a phyllosilicate of potassium, iron in both oxidation states, aluminum and hydroxide with the formula: K(Mg, Fe2+)(Fe3+, Al)[Si4O10](OH)2. It was named after the French word ‘celadon’, meaning sea green, in allusion to its color. It crystallizes in the monoclinic system and usually forms massive aggregates of prismatic crystallites or in dull clay masses. It is soft with a Mohs hardness of 2 and a specific gravity of 3.

It was first described in 1847 on Monte Baldo, near Verona, Italy. The name is from the French celadon, for sea-green. It is one of two minerals, along with glauconite, used in making the pigment known as green earth.

General Information

  • Category: Micas Phyllosilicate
  • Formula: K(Mg,Fe2+)(Fe3+,Al)[Si4O10](OH)2.
  • Crystal system: Monoclinic
  • Crystal class: Spheroidal (2) (same H-M symbol)

Properties

Celadonite can be identified in the field by its color variations, such as gray-green and bluish-green. Its translucent to opaque form has {001} perfect cleavage. This mineral has an earthy luster with greenish-white streaks. The density of celadonite is 2.95 – 3.05 g/cm3, with a hardness of 2 – approximate to gypsum. It has clay-like fractures.

  • Lustre: Waxy, Dull, Earthy
  • Transparency: Translucent
  • Color: Blue-green, olive green, apple green
  • Hardness: 2 on Mohs scale
  • Tenacity: Fragile
  • Cleavage: Perfect perfect on {001}
  • Comment: Friable to unctuous
  • Density: 2.95 – 3.05 g/cm3 (Measured) and 3 g/cm3 (Calculated)

Occurrence

Celadonite replaces primary ferromagnesian silicate minerals in altered intermediate to mafic volcanic rocks. It occurs under low-grade zeolite facies metamorphism, and as amygdule fillings in basalts or andesites. Typically occurs as dull gray-green to bluish green masses. It forms vesicle fillings and linings in altered basaltic lavas.

It is often associated with minerals such as montmorillonite, calcite, clinoptilolite, laumontite, prehnite, heulandite, chlorite, and quartz.

 

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