Greenalite is a mineral in the kaolinite- serpentine group with the chemical composition (Fe²⁺,Fe³⁺)_2-3Si₂O₅(OH)₄.Handbook of Mineralogy
/ref>Sleep N.H., Bird D.K. (2007): Niches of the pre-photosynthetic biosphere and geologic preservation of Earth’s earliest ecology.

Geobiology Geobiology is a field of scientific research that explores the interactions between the physical Earth and the biosphere. It is a relatively young field, and its borders are fluid. There is considerable overlap with the fields of ecology, evolutio ...

5, 101-117 It is a member of the serpentine group.

Occurrence

Greenalite was first described in 1903 for an occurrence in the Mesabi Range near Biwabik,

St. Louis County, Minnesota St. Louis County is a county located in the Arrowhead Region of the U.S. state of Minnesota. As of the 2020 census, the population was 200,231. Its county seat is Duluth. It is the largest county in Minnesota by land area, and the largest i ...

and named for its green color. Greenalite occurs as a primary phase in

banded iron formation Banded iron formations (also known as banded ironstone formations or BIFs) are distinctive units of sedimentary rock consisting of alternating layers of iron oxides and iron-poor chert. They can be up to several hundred meters in thickness a ...

s. Rocks which contain greenalite are usually bright green, pale green or pale brown. Greenalite occurs with quartz, stilpnomelane, siderite, chamosite,

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...

and minnesotaite. It is commonly oolitic.

References

Phyllosilicates Monoclinic minerals Minerals in space group 8 {{silicate-mineral-stub