sedimentary
Glauconitic Sandstone (Greensand)
Glauconitic Sandstone (Iron-potassium phyllosilicate mineral: (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2)
Hardness: 2-3 (Mohs scale), Color: Dull green to dark olive green, Luster: Dull/Earthy, Crystal Structure: Monoclinic (usually found as grains), Specific Gravity: 2.4-2.85
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Physical properties
Hardness: 2-3 (Mohs scale), Color: Dull green to dark olive green, Luster: Dull/Earthy, Crystal Structure: Monoclinic (usually found as grains), Specific Gravity: 2.4-2.85
Formation & geological history
Formed in marine environments through the alteration of minerals and organic matter on the shallow sea floor in reducing conditions. Often found in Cretaceous or Tertiary period strata.
Uses & applications
Used historically as a slow-release potassium fertilizer in agriculture, as a water softener, and occasionally as a source of pigment for stone finishes.
Geological facts
Glauconite is considered an indicator of marine deposition and a slow rate of sediment accumulation. It is often referred to as 'green earth' by artists.
Field identification & locations
Identify by its distinctive dull green hue and sandy/crumbly texture. Common in coastal plain areas like New Jersey, USA, or the South Downs in the UK. Collectors should look for the characteristic 'olive' grain appearance.
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