Greenalite is a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

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 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 ...

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

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

, stilpnomelane,

siderite Siderite is a mineral composed of iron(II) carbonate (FeCO3). It takes its name from the Greek word σίδηρος ''sideros,'' "iron". It is a valuable iron mineral, since it is 48% iron and contains no sulfur or phosphorus. Zinc, magnesium and ...

chamosite Chamosite is the Fe2+end member of the chlorite group. A hydrous aluminium silicate of iron, which is produced in an environment of low to moderate grade of metamorphosed iron deposits, as gray or black crystals in oolitic iron ore. Like other ...

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