sedimentary
Glauconitic Sanstone (Glauconite)
Glauconite ((K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2)
Hardness: 2 Mohs; Color: Dull green, olive green, or blackish green; Luster: Dull to pearly; Crystal Structure: Monoclinic; Cleavage: Perfect basal; SG: 2.4-2.95
- Hardness
- 2 Mohs
- Color
- Dull green, olive green, or blackish green
- Luster
- Dull to pearly
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Physical properties
Hardness: 2 Mohs; Color: Dull green, olive green, or blackish green; Luster: Dull to pearly; Crystal Structure: Monoclinic; Cleavage: Perfect basal; SG: 2.4-2.95
Formation & geological history
Formed in marine environments through the alteration of minerals like mica and fecal pellets on the seabed during periods of slow sedimentation. Typically found in deposits from the Paleozoic to the present.
Uses & applications
Used primarily as a soil conditioner and source of potassium (greensand) in organic farming. Historically used as a green pigment for paints.
Geological facts
Glauconite is a 'facies indicator' meaning its presence tells geologists that the area was once a shallow, marine environment with slow sediment accumulation. It is often responsible for the green color in 'greensand' formations.
Field identification & locations
Identified in the field by its distinct green color and sandy or pelletal texture. It is often soft and can be crushed to a powder. Found in coastal regions like New Jersey (USA), England, and Australia.
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