sedimentary

Glauconite (Greensand)

Glauconite (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2

AI-generated identification · may be incorrect

Hardness: 2 Mohs; Color: Dull green, olive green, or blue-green; Luster: Dull to earthy; Crystal Structure: Monoclinic; Cleavage: Perfect mica-like; Specific Gravity: 2.4-2.95

Hardness: 2 Mohs
Color: Dull green, olive green, or blue-green
Luster: Dull to earthy

Identified June 4, 2026More sedimentary →

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Physical properties

Hardness: 2 Mohs; Color: Dull green, olive green, or blue-green; Luster: Dull to earthy; Crystal Structure: Monoclinic; Cleavage: Perfect mica-like; Specific Gravity: 2.4-2.95

Formation & geological history

Formed in marine environments on the continental shelf through slow accumulation and shallow-water chemical alteration of fecal pellets and organic matter. Typically found in Cretaceous and Tertiary marine sediments.

Uses & applications

Used as an organic fertilizer (greensand) for potassium, a water softener (ion exchange), and historically as a green pigment in paints.

Geological facts

Glauconite is an 'atypical' mica that grows directly in salt water and is a key indicator of shallow marine depositional environments in the geological record.

Field identification & locations

Identified by its distinctive dull green color and crumbly texture. Often found in sandy formations ('greensands') along coastal regions like the US Eastern Seaboard, particularly New Jersey and Delaware.