sedimentary

Glauconitic Sandstone (Greensand)

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

AI-generated identification · may be incorrect

Hardness: 2-7 (varies based on cementation); Color: Dull green, olive, or grayish-blue; Luster: Earthy to dull; Crystal structure: Monoclinic (microcrystalline grains); Cleavage: Perfect basal (not visible in mass); Specific Gravity: 2.4-2.85.

Hardness: 2-7 (varies based on cementation)
Color: Dull green, olive, or grayish-blue
Luster: Earthy to dull

Identified February 9, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine continental shelf environments under reducing conditions. It is primarily composed of the mineral glauconite, which develops through the chemical alteration of mica or organic matter in low-oxygen seawater. Ages range from the Paleozoic to Cenozoic eras.

Uses & applications

Used as a slow-release natural fertilizer (potash source), a soil conditioner, a water softener (due to ion-exchange properties), and occasionally as a low-grade construction aggregate.

Geological facts

Glauconite is often referred to as 'Greensand.' Because it forms specifically in marine environments, its presence is a key tool for geologists to identify ancient sea levels and marine transgressive sequences in the rock record.

Field identification & locations

Identify in the field by its characteristic green hue and sandy, granular texture that can sometimes rub off on the hands. Commonly found in coastal plains, such as the Atlantic Coast of the US, England, and Australia. Collectors look for well-preserved fossil inclusions often found within these beds.