igneous

Celadonite in Amygdaloidal Basalt

K(Mg,Fe2+)(Fe3+,Al)Si4O10(OH)2 (Celadonite mineral) within a Basalt matrix

Hardness: 2 (celadonite) / 5-6 (basalt matrix); Color: Dull to bright olive-green; Luster: Earthy to pearly; Crystal structure: Monoclinic (usually found as massive/earthy coatings); Specific gravity: 2.9-3.0.

Hardness: 2 (celadonite) / 5-6 (basalt matrix)
Color: Dull to bright olive-green
Luster: Earthy to pearly

Identified February 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the hydrothermal alteration of mafic minerals (like olivine or pyroxene) or volcanic glass within the vesicles (gas bubbles) of cooling basaltic lava flows. Most typically associated with low-grade metamorphism.

Uses & applications

Used historically as a green pigment ('terra verte' or Green Earth) in artistic painting. Currently valued as mineral specimens for collectors and used in petrological studies of volcanic environments.

Geological facts

Celadonite is a member of the mica group. It is a key indicator of low-temperature hydrothermal activity in seafloor and terrestrial lava systems. It is what gives 'green basalt' or 'greenstone' its distinctive hue.

Field identification & locations

Identify in the field by looking for soft, green, earthy fillings or coatings inside the cavities (amygdules) of dark, vesicular volcanic rocks. Commonly found in the Pacific Northwest (USA), India (Deccan Traps), and the Faroe Islands.

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