sedimentary

Glauconite (Greensand)

Glauconite ((K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2)

AI-generated identification · may be incorrect

Hardness: 2 Mohs; Color: dull green to bluish-green; Luster: dull to earthy; Structure: monoclinic (often found as small rounded pellets); Cleavage: perfect (rarely seen in grains)

Hardness: 2 Mohs
Color: dull green to bluish-green
Luster: dull to earthy

Identified July 5, 2026More sedimentary →

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Physical properties

Hardness: 2 Mohs; Color: dull green to bluish-green; Luster: dull to earthy; Structure: monoclinic (often found as small rounded pellets); Cleavage: perfect (rarely seen in grains)

Formation & geological history

Formed in marine environments through slow sedimentation in shallow waters; typically associated with continental shelf deposits and dates from the Cambrian to the present.

Uses & applications

Used as a soil conditioner and slow-release potassium fertilizer; historically used as a green pigment and for water softening via ion exchange.

Geological facts

Glauconite is an 'authentigenic' mineral, meaning it forms in place on the seafloor. Its presence in a rock formation is a strong indicator of a slow rate of sedimentation in a marine environment.

Field identification & locations

Identify by its distinctive earthy green color and tendency to crumble into smaller grains. Commonly found in 'Greensand' formations in New Jersey, USA, and along the English coast.