sedimentary

Glauconite (Green Sandstone)

Glauconite (K,Na)(Fe,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 (micaceous); Cleavage: Perfect basal; Specific gravity: 2.4-2.9.

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

Identified May 30, 2026More sedimentary →

Explore Glauconite (Green Sandstone) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 2 Mohs; Color: Dull green, olive green, or blue-green; Luster: Dull to earthy; Crystal structure: Monoclinic (micaceous); Cleavage: Perfect basal; Specific gravity: 2.4-2.9.

Formation & geological history

Formed in marine environments through the alteration of minerals like biotite or fecal pellets in shallow continental shelf waters. Often found in Cretaceous and Tertiary seafloor deposits.

Uses & applications

Used historically as a green pigment for paint, as a water softener due to ion-exchange properties, and widely used today as a natural slow-release organic fertilizer.

Geological facts

Glauconite is an indicator of slow sedimentation rates in marine environments. When it is found in high concentrations, the rock is often called a 'Greensand'.

Field identification & locations

Identify in the field by its distinctive green color and crumbly, sandy texture. It usually occurs as small rounded pellets or grains within a sandstone or clay matrix. Found heavily in the Atlantic Coastal Plain of the USA.