sedimentary
Glauconite (Greensand)
(K, Na)(Fe3⁰, Al, Mg)₂(Si, Al)₄O₁₀(OH)₂
Hardness: 2.0; Color: dull green to bluish-green; Luster: earthy to pearly; Crystal structure: monoclinic; Cleavage: perfect (micaceous); Specific Gravity: 2.4 - 2.95.
- Hardness
- 2
- Color
- dull green to bluish-green
- Luster
- earthy to pearly
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Physical properties
Hardness: 2.0; Color: dull green to bluish-green; Luster: earthy to pearly; Crystal structure: monoclinic; Cleavage: perfect (micaceous); Specific Gravity: 2.4 - 2.95.
Formation & geological history
Glauconite forms in marine environments through the alteration of minerals (like mica) or organic matter in shallow continental shelf waters. It typically dates from the Cambrian period to the present.
Uses & applications
Used primarily as a soil conditioner and organic fertilizer due to its potassium content. It was historically used as a pigment (green earth) in paintings and is used in water softening systems.
Geological facts
Glauconite is a 'facies indicator,' meaning its presence tells geologists that the area was once a shallow, slow-sedimenting marine environment. It is often found as small rounded pellets.
Field identification & locations
Identify by its distinctive dull green color and crumbly texture. Search in coastal plains or sedimentary rock outcrops, notably in the New Jersey coastal plain or certain Cretaceous formations.
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