sedimentary

Glauconitic Sandstone

Glauconitic Quartz Arenite (with K,Mg,Fe,Al silicate hydroxide)

Hardness: 2-3 (glauconite grains), 7 (quartz matrix); Color: Olive green to grey-green; Luster: Dull to earthy; Texture: Granular, friable; Structure: Often found as pellets or rounded grains within a sandy matrix.

Hardness: 2-3 (glauconite grains), 7 (quartz matrix)
Color: Olive green to grey-green
Luster: Dull to earthy

Identified July 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine environments on continental shelves through the slow chemical alteration of organic matter and detrital minerals like biotite under reducing conditions. Usually Cretaceous to Eocene in age.

Uses & applications

Used primarily as a soil conditioner and source of potassium (greensand) in organic farming, as a water softener, and historically as a green pigment.

Geological facts

Glauconite is known as 'greensand' and is considered an indicator mineral for marine depositional environments. It takes thousands of years of stable marine conditions for these green silicate grains to form.

Field identification & locations

Look for a dull green, granular appearance that is relatively soft and stains fingers slightly green when crushed. Commonly found in coastal plains and sedimentary basins like the London Basin or the US Atlantic coastal plain.

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Sandstone or Siltstone

Arenite (if sandstone)

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