Celadonite

Celadonite is a mica group mineral, a phyllosilicate of potassium, iron in both oxidation states, aluminium and hydroxide with formula: K(Mg,Fe)(Fe,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.