Greenalite

{{Short description|Phyllosilicate mineral in the kaolinite-serpentine group}} {{infobox mineral | name = Greenalite | image = Galena siderite Cartagena.jpg | alt = | caption = Greenalite (green) with galena and siderite, from Spain | category = Phyllosilicate minerals | group = Kaolinite-Serpentine group | formula = (Fe2+,Fe3+)2-3Si2O5(OH)4 | IMAsymbol = Gre<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = | strunz = 9.ED.15 | dana = | system = Monoclinic | class = Domatic (m) (same H-M symbol) | symmetry = ''Cm'' | unit cell = a = 5.54, b = 9.55 c = 7.44 [Å]; β = 104.2°; Z = 2 | color = Green, light yellow-green | colour = | habit = Rare minute crystals, rounded grains common; as porphyroblasts, oolites | twinning = | cleavage = None | fracture = | tenacity = | mohs = 2.5 | luster = Dull, earthy | streak = Greenish-gray | diaphaneity = Translucent to subopaque | gravity = 2.85 - 3.15 | density = | polish = | opticalprop = Biaxial (+) | refractive = nα = 1.650 - 1.675 nβ = 1.674 nγ = 1.674 | birefringence = δ = 0.024 | pleochroism = X = pale yellow, Y and Z = green | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = Magnetic | references = <ref name=Handbook/><ref name=Mindat>[http://www.mindat.org/min-1745.html Greenalite on Mindat.org]</ref><ref name=Webmin>[http://www.webmineral.com/data/Greenalite.shtml Greenalite on Webmineral]</ref> }} '''Greenalite''' is a mineral in the kaolinite-serpentine group<ref name=Mindat/> with the chemical composition (Fe2+,Fe3+)2-3Si2O5(OH)4.<ref name=Handbook>[http://rruff.geo.arizona.edu/doclib/hom/greenalite.pdf Handbook of Mineralogy]</ref><ref>Sleep N.H., Bird D.K. (2007): Niches of the pre-photosynthetic biosphere and geologic preservation of Earth’s earliest ecology. Geobiology 5, 101-117</ref>

==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.<ref name=Mindat/>

Greenalite occurs as a primary mineral in banded iron formations. Rocks which contain greenalite are usually bright green, pale green or pale brown. Greenalite occurs with quartz, stilpnomelane, siderite, chamosite, pyrite and minnesotaite. It is commonly oolitic.<ref name=Handbook/>

== Effect on early life == Greenalite, which is common in Archean rocks, formed rapidly in Archean seawater removing zinc, copper and vanadium in the process. This left the seawater rich in manganese, molybdenum, and cadmium, which are metals favoured by lifeforms at that time. Experiments have shown that the removed metals would have been removed permanently, having a significant effect on early seawater.<ref>{{Cite web |title=Recreation of ancient seawater reveals which nutrients shaped the evolution of early life |publisher=University of Oxford |date=13 November 2023 |url=https://www.ox.ac.uk/news/2023-11-13-recreation-ancient-seawater-reveals-which-nutrients-shaped-evolution-early-life |access-date=2023-11-20 |website=www.ox.ac.uk |language=en}}</ref>

==References== {{reflist}}

Category:Kaolinite-Serpentine group Category:Monoclinic minerals Category:Minerals in space group 8