sedimentary
Glauconitic Sandstone (Greensand)
Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2
Hardness: 2-3 (Mohs scale), Color: Dull green, olive green, or gray-green, Luster: Dull/Earthy, Crystal Structure: Monoclinic (micaceous), Cleavage: Perfect basal (usually appears as rounded crumbs), Specific Gravity: 2.4-2.9.
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Physical properties
Hardness: 2-3 (Mohs scale), Color: Dull green, olive green, or gray-green, Luster: Dull/Earthy, Crystal Structure: Monoclinic (micaceous), Cleavage: Perfect basal (usually appears as rounded crumbs), Specific Gravity: 2.4-2.9.
Formation & geological history
Formed in marine environments slow-depositing continental shelf settings through the alteration of detrital mica or fecal pellets. It is typically found in strata from the Cambrian to the Cenozoic eras.
Uses & applications
Used primarily as a soil conditioner (Green Sand) to provide potassium and iron, as a water softener, and historically as a pigment. It is also used in filtering systems due to ion exchange properties.
Geological facts
Glauconite is an 'atypical' mineral because it forms almost exclusively in marine waters. Its presence in a rock layer is a strong indicator of a slow rate of sedimentation in a shallow sea environment.
Field identification & locations
Identify in the field by its distinct dull green color and crumbly texture. It often colors entire sandstone beds green. Found commonly in the Atlantic Coastal Plain of the USA, particularly New Jersey, and parts of the UK.
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