Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable[5] and has very low weathering resistance.

[8] Normally, glauconite is considered a diagnostic mineral indicative of continental shelf marine depositional environments with slow rates of accumulation and gradational boundaries.

For instance, it appears in Jurassic/lower Cretaceous deposits of greensand, so-called after the coloration caused by glauconite, its presence gradually lessening further landward.

It develops as a consequence of diagenetic alteration of sedimentary deposits at the surface, bio-chemical reduction and subsequent mineralogical changes affecting iron-bearing micas such as biotite, and is also influenced by the decaying process of organic matter degraded by bacteria in marine animal shells.

It is used for soil conditioning in both organic and non-organic farming, whether as an unprocessed material (mixed in adequate proportions) or as a feedstock in the synthesis of commercial fertilizer powders.

In Brazil, greensand refers to a fertilizer produced from a glauconitic siltstone unit belonging to the Serra da Saudade Formation, Bambuí Group, of Neoproterozoic/Ediacaran age.

The sedimentary provenance is from supracrustal felsic elements in a continental margin environment with acid magmatic arc (foreland basin).

In the wind farm industry off the coasts of Massachusetts, New York and New Jersey, glauconite-rich sands of Cretaceous to Paleogene age found in the seabed have become a hazard to the installation of monopiles used for turbine foundation.