sedimentary
Glauconitic Sandstone
Glauconitic arenite (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2
Hardness: 2-3 (Mohs scale), Color: Dull olive green to dark green, Luster: Earthy/Dull, Crystal structure: Monoclinic (micaceous grains), Cleavage: Perfect basal (rarely seen in grain form), Specific gravity: 2.4-2.85
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Physical properties
Hardness: 2-3 (Mohs scale), Color: Dull olive green to dark green, Luster: Earthy/Dull, Crystal structure: Monoclinic (micaceous grains), Cleavage: Perfect basal (rarely seen in grain form), Specific gravity: 2.4-2.85
Formation & geological history
Formed in marine continental shelf environments through slow sedimentation in reducing conditions. It is frequently associated with fecal pellets or shells and is most common in Cretaceous and Cenozoic strata.
Uses & applications
Historically used as a green pigment for paints, as a soil conditioner (greensand), and as a water softener due to its ion-exchange properties.
Geological facts
Glauconite is often referred to by gardeners as 'Greensand.' It is an indicator of slow deposition rates in ancient marine environments and is used by geologists for radioactive dating of sedimentary sequences.
Field identification & locations
Identify in the field by its distinct green color and crumbly, sandy texture. It often leaves a green streak if crushed. Commonly found in coastal plain regions like the Cretaceous formations of New Jersey or the UK.
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