sedimentary
Glauconitic Sandstone (Greensand)
Glauconitic Sandstone ((K, Na)(Fe3+, Al, Mg)2(Si, Al)4O10(OH)2)
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 More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
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.
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.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary