mineral

Glauconite

Glauconite (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2

AI-generated identification · may be incorrect

Hardness: 2.0; Color: Blue-green, olive-green; Luster: Pearly to dull; Crystal structure: Monoclinic; Cleavage: Perfect mica-like; Specific Gravity: 2.4-2.95

Hardness: 2
Color: Blue-green, olive-green
Luster: Pearly to dull

Identified May 30, 2026More mineral →

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Physical properties

Hardness: 2.0; Color: Blue-green, olive-green; Luster: Pearly to dull; Crystal structure: Monoclinic; Cleavage: Perfect mica-like; Specific Gravity: 2.4-2.95

Formation & geological history

Formed in marine continental shelf environments through the slow diagenetic alteration of organic matter, mica, or clay minerals in reducing conditions. Most common in sedimentary rocks from the Cambrian to Holocene.

Uses & applications

Used primarily as a soil conditioner and source of potassium/iron in organic fertilizers. Historically used as a pigment (green earth) and for water softening via ion exchange.

Geological facts

Glauconite is often found in 'greensands'. It is a key indicator of slow sedimentation rates in marine environments and is used by geologists for radioactive dating of sedimentary sequences.

Field identification & locations

Identify in the field by its distinctive dull green rounded pellets (granules) and its tendency to crumble into a green powder when crushed. Commonly found in coastal sedimentary deposits.