sedimentary

Glauconitic Sandstone

Glauconitic Sandstone (complex silicate formula: (K,Na)(Fe,Al,Mg)2(Si,Al)4O10(OH)2)

AI-generated identification · may be incorrect

Hardness: 2-3 (for individual grains), 6-7 (if silicified matrix); Color: dull green to grayish-green; Luster: earthy to dull; Crystal structure: monoclinic (micaceous); Specific Gravity: 2.4 - 2.85.

Hardness: 2-3 (for individual grains), 6-7 (if silicified matrix)
Color: dull green to grayish-green
Luster: earthy to dull

Identified March 24, 2026More sedimentary →

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Physical properties

Hardness: 2-3 (for individual grains), 6-7 (if silicified matrix); Color: dull green to grayish-green; Luster: earthy to dull; Crystal structure: monoclinic (micaceous); Specific Gravity: 2.4 - 2.85.

Formation & geological history

Formed in marine shelf environments with slow rates of accumulation, typically during high sea-level stands. It is an authigenic mineral that forms via the modification of fecal pellets or debris of other minerals in reducing environments.

Uses & applications

Used historically as a green pigment ('green earth') in painting, as a water softener due to its ion-exchange properties, and in agriculture as a slow-release potassium fertilizer (greensand).

Geological facts

The presence of glauconite is often used by geologists as an indicator of a marine depositional environment and a slow rate of sedimentation. It is frequently associated with offshore continental shelf deposits.

Field identification & locations

Identify in the field by its distinct dull olive-green color and 'sandy' feel. It is often found in Cretaceous or Tertiary marine strata. Collectors should look for 'greensand' beds in coastal regions like the New Jersey coastal plain or parts of the UK.