{{Short description|Phyllosilicate mineral}} {{Infobox mineral | name = Cymrite | category = Phyllosilicate minerals | boxwidth = | boxbgcolor = | image = Cymrite-352204.jpg | imagesize = | caption = Cymrite (2.2 x 1.6 x 1.6 cm) | formula = BaAl<sub>2</sub>Si<sub>2</sub>(O,OH)<sub>8</sub>·(H<sub>2</sub>O) | IMAsymbol = Cym<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> | system = Monoclinic | class = Domatic (m) <br /><small>(same H-M symbol)</small> | symmetry = ''Pm'' | unit cell = a = 5.32 Å, b = 36.6 Å, <br />c = 7.66 Å; β = 90°; Z = 2 | color = Brown, greenish, colorless | habit = Micacious, sheet-like, pseudohexagonal, also fibrous | twinning = | cleavage = Perfect on {001}, good on {110} | fracture = Uneven | tenacity = Brittle | mohs = 2-3 | luster = Silky, Vitreous | refractive = nα = 1.611 nβ = 1.619 nγ = 1.621 | opticalprop = Biaxial (-) | 2V = 0-5° | birefringence = δ = 0.010 | pleochroism = | streak = White | gravity = 3.49 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent | other = | references = <ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/cymrite.pdf Handbook of Mineralogy]. Accessed October 15, 2010.</ref><ref>{{cite web |url=http://www.museumwales.ac.uk/en/mineralogy/database/?mineral=209 |title= Mineral Database | National Museum Wales|website=www.museumwales.ac.uk |access-date=October 2, 2010}}{{title missing|date=May 2022}}</ref><ref name=Webmin>[http://www.webmineral.com/data/Cymrite.shtml Webmineral data] Accessed September 5, 2010</ref><ref name=Mindat>[http://www.mindat.org/min-1205.html Mindat.org]. Accessed September 27, 2010</ref><ref name=EMG>O'Donoghue, M. (1976) The Encyclopedia of Minerals and Gemstones. Orbis Publishing, London.</ref><ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cymrite Mineralienatlas]</ref> }}
'''Cymrite''' is a silicate mineral with the chemical formula BaAl<sub>2</sub>Si<sub>2</sub>(O,OH)<sub>8</sub>·H<sub>2</sub>O.<ref name=Mindat/> The mineral is named for Cymru, which is the Welsh word for Wales.<ref name=Webmin/>
Cymrite, with perfect cleavage and a monoclinic crystalline system, falls in the silicate group.<ref name=Mindat/> Silicates are formed of Silicon and Oxygen bonding together to form tetrahedra.<ref name=EMG/> The symmetry of Cymrite is classified as having a mirror plane. It has a moderate relief, meaning the contrast between the mineral and the epoxy of a thin section makes cymrite easily visible. The birefringence of the mineral is 0.01.<ref name=Mindat/> Cymrite, being monoclinic is anisotropic with two optic axes.
==Occurrence== Cymrite was discovered in Wales but is found in other areas throughout the United States, Africa, Greece and other parts of Europe. It occurs in generally high temperature-pressure areas such as the hydrothermal manganese silicate ore that makes up the Benalt Mine in Wales and in manganese rock that has undergone high-pressure metamorphism found in Greece.<ref name=HBM/> It is important to geologists because of its limited occurrence, when cymrite is present on a rock it indicates that the rock, at some point, must have experienced high pressure and temperature.
== References == {{Reflist}}
Category:Phyllosilicates Category:Barium minerals Category:Monoclinic minerals Category:Minerals in space group 6