Glauconite (appearing as Green Earth / Celadonite in host rock)
Glauconite or Celadonite (Mica group species) · Mineral Specimen / Industrial Pigment Mineral
Crystal System
Monoclinic; commonly occurs in earthy, granular, or massive cryptocrystalline habits.
Mineral Group
Silicates; Phyllosilicates (Mica Group)
Chemical Formula
(K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2
Formation Process
Sedimentary/Authigenic (marine environments with low oxygen) or Secondary hydrothermal alteration of basaltic glass and ferro-magnesian minerals.
About This Crystal
An earthy, matte-textured mineral in shades of olive-green to forest-green, appearing here on a brownish sedimentary or volcanic host rock. It is opaque with a dull, waxy to earthy luster and lacks visible crystal faces without magnification.
Physical Characteristics
Color: Green to dark green; Streak: Greenish; Fracture: Uneven; Specific Gravity: 2.4 - 2.85; Luster: Dull or earthy; Tenacity: Brittle; Cleavage: Perfect on {001} (rarely visible in massive forms).
Optical Properties
Biaxial negative; Refractive index approx. 1.590 to 1.645; Non-fluorescent; Lacks transparency and significant dispersion.
Hardness & Durability
Origin Region
Common in marine sedimentary rocks worldwide; notable deposits in the United Kingdom, New Jersey (USA), and various European basaltic regions.
Hardness & Durability
Mohs Hardness: 2.0; very soft and fragile. Low durability; can be scratched with a fingernail or copper coin.
Care & Maintenance
Extremely fragile; store in a dry, stable environment away from humidity. Clean only with a soft, dry brush; do not use water, ultrasonics, or chemicals which may dissolve or crumble the specimen.
Rarity & Value
Common; low monetary value as a specimen. Its value is primarily industrial (fertilizers, water softeners) or historical (pigment production).
Special Characteristics
Known for its use as 'Green Earth' (Terra Verte) in art; occasionally contains tiny sparkling particles of associated zeolites or quartz.
Lore & History
Historically used since ancient Roman times as a pigment in wall paintings (frescoes). In metaphysical lore, green earth minerals are associated with grounding, connection to the natural world, and stabilizing the heart chakra.