{{Infobox mineral | name = Cyanotrichite | boxwidth = | boxbgcolor = | image = Cyanotrichite-Malachite-249320.jpg | imagesize = 260px | alt = | caption = Radiating sprays of cyanotrichite needles on matrix from the old Grand Canyon Mine now within Grand Canyon National Park (size: 3.8 × 3.7 × 1.2 cm) | category = Sulfate minerals | formula = Cu<sub>4</sub>Al<sub>2</sub>[(OH)<sub>12</sub><nowiki>|</nowiki>SO<sub>4</sub>]·2H<sub>2</sub>O | IMAsymbol=Cya<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 = 7.DE.10 | dana = | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''C2/m'' | unit cell = a = 10.16 Å, b = 12.61 Å, <br/>c = 2.9 Å; Z = 1 | color = Sky-blue, azure-blue | colour = | habit = Acicular crystals and fibrous aggregates; incrustations | twinning = | cleavage = | fracture = Uneven | tenacity = | mohs = 1–3 | luster = Silky | streak = Light blue | diaphaneity = Transparent to translucent | gravity = 2.76 | density = | polish = | opticalprop = Biaxial (+) | refractive = n<sub>α</sub> = 1.588 n<sub>β</sub> = 1.617 n<sub>γ</sub> = 1.655 | birefringence = δ = 0.067 | pleochroism = X = colorless; Y = pale blue; Z = bright blue | 2V = Measured: 82° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = <ref name=HBM>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Cyanotrichite |url=https://www.handbookofmineralogy.org/pdfs/cyanotrichite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=3 August 2022 |date=2005}}</ref> | var1 = Polianite | var1text = pseudomorphic after manganite<ref>{{mindat|id=6101|title=Polianite|access-date=4 August 2022}}</ref><ref name=Mindat>{{mindat|id=1203|title=Cyanotrichite|access-date=4 August 2022}}</ref><ref name=Webmin>{{Cite web|last1=Barthelmy|first1=David|year=2014|url=https://www.webmineral.com/data/Cyanotrichite.shtml|access-date=4 August 2022|title = Cyanotrichite Mineral Data|website=Webmineral.com}}</ref><ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cyanotrichite Mineralienatlas]</ref> }}
'''Cyanotrichite''' is a hydrous copper aluminium sulfate mineral with formula Cu<sub>4</sub>Al<sub>2</sub>[(OH)<sub>12</sub>|SO<sub>4</sub>]·2H<sub>2</sub>O, also known as '''lettsomite'''. Cyanotrichite forms velvety radial acicular crystal aggregates of extremely fine fibers. It crystallizes in the monoclinic system and forms translucent bright blue acicular crystal clusters or drusey coatings. The Mohs hardness is 2 and the specific gravity ranges from 2.74 to 2.95. Refractive indices are nα = 1.588 nβ = 1.617 nγ = 1.655.
==Occurrence and discovery== It is an oxidation product of primary copper mineralization in a weathering environment with abundant aluminium and sulfate. Associated minerals include brochantite, spangolite, chalcophyllite, olivenite, tyrolite, parnauite, azurite and malachite.<ref name=HBM/>
The main deposits are Cap la Garrone in the Var (France), Romania and Arizona (US).
It was first described in 1839 from Moldova Nouă, Banat, Romania. The name is from Greek ''kyaneos'' for "blue" and ''triches'' for "hair" referring to the typical color and habit. Its earlier name, Lettsomite, is taken from the name of William Garrow Lettsom (1805–1887), co-author of the 1858 ''Manual of the Mineralogy of Great Britain and Ireland''.
==References== {{reflist}} * Palache, C., H. Berman, and C. Frondel (1951) ''Dana’s System of Mineralogy'', (7th edition), v. II, p. 578–579. [https://rruff.geo.arizona.edu/doclib/hom/cyanotrichite.pdf PDF file] *[https://web.archive.org/web/20060509222414/http://mineral.galleries.com/minerals/sulfates/cyanotri/cyanotri.htm Mineral galleries]
{{commons category|Cyanotrichite }}
Category:Copper(II) minerals Category:Aluminium minerals Category:Sulfate minerals Category:Monoclinic minerals Category:Minerals in space group 12