sedimentary

Glauconitic Sandstone

Glauconitic Sandstane (containing K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2)

Hardness: 2-3 (for individual glauconite grains but the rock matrix varies); Color: Dull olive-green to dark green; Luster: Earthy to dull; Crystal structure: Monoclinic (microcrystalline grains); Specific gravity: 2.4 - 2.95.

Color: Dull olive-green to dark green
Luster: Earthy to dull

Identified June 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine environments through slow sedimentation in shallow shelf waters (50-200 meters deep) during periods of slow deposition. It is often associated with the 'Greensand' formations of the Cretaceous and Eocene periods.

Uses & applications

Historically used as a soil conditioner and fertilizer due to its potassium and iron content. It is also used in water softening systems and as a slow-release green-colored pigment.

Geological facts

Glauconite is a 'facies indicator' meaning its presence tells geologists the rock was formed in a marine environment with very low oxygen and slow sediment accumulation. It is responsible for the famous 'Greensand' cliffs in areas like the Isle of Wight.

Field identification & locations

Identify in the field by its distinct dull green color and sandy, granular texture that rub off on hands if the specimen is friable. Commonly found in coastal sedimentary formations and fossil beds. It often contains marine fossils like shark teeth or shells.

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