Celadonite

Celadonite
Celadonite is the green mineral that forms the matrix in this specimen, which also features larger calcite rhombs, glassy, colorless, apophyllite crystals and a single, pearlescent, tan, bladed stilbite crystal cluster at upper left-center. From Jalgaon District, Maharashtra, India. Size: 14.0 x 9.0 x 3.9 cm.
General
Category	Micas Phyllosilicate
Formula (repeating unit)	K(Mg,Fe2+)(Fe3+,Al)[Si4O10](OH)2
Crystal system	Monoclinic
Crystal class	Spheroidal (2) (same H-M symbol)
Space group	C2
Identification
References

Celadonite is a mica group mineral, a phyllosilicate of potassium, iron in both oxidation states, aluminium and hydroxide with formula: K(Mg,Fe²⁺)(Fe³⁺,Al)[Si₄O₁₀](OH)₂.

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. Typically occurs as dull gray-green to bluish green masses. It forms vesicle fillings and linings in altered basaltic lavas.

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.