Cymrite

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title: "Cymrite" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["phyllosilicates", "barium-minerals", "monoclinic-minerals", "minerals-in-space-group-6"] description: "Phyllosilicate mineral" topic_path: "general/phyllosilicates" source: "https://en.wikipedia.org/wiki/Cymrite" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Phyllosilicate mineral ::

::data[format=table title="Infobox mineral"]

Field	Value
name	Cymrite
category	Phyllosilicate minerals
image	Cymrite-352204.jpg
caption	Cymrite (2.2 x 1.6 x 1.6 cm)
formula	BaAl2Si2(O,OH)8·(H2O)
IMAsymbol	Cym
system	Monoclinic
class	Domatic (m)
(same H-M symbol)
symmetry	Pm
unit cell	a = 5.32 Å, b = 36.6 Å,
c = 7.66 Å; β = 90°; Z = 2
color	Brown, greenish, colorless
habit	Micacious, sheet-like, pseudohexagonal, also fibrous
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
streak	White
gravity	3.49
diaphaneity	Transparent to translucent
references
::

| name = Cymrite | category = Phyllosilicate minerals | boxwidth = | boxbgcolor = | image = Cymrite-352204.jpg | imagesize = | caption = Cymrite (2.2 x 1.6 x 1.6 cm) | formula = BaAl2Si2(O,OH)8·(H2O) | IMAsymbol = Cym | system = Monoclinic | class = Domatic (m) (same H-M symbol) | symmetry = Pm | unit cell = a = 5.32 Å, b = 36.6 Å, 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 =

Cymrite is a silicate mineral with the chemical formula BaAl2Si2(O,OH)8·H2O. The mineral is named for Cymru, which is the Welsh word for Wales.

Cymrite, with perfect cleavage and a monoclinic crystalline system, falls in the silicate group. Silicates are formed of Silicon and Oxygen bonding together to form tetrahedra. 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. 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. 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

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. [http://rruff.geo.arizona.edu/doclib/hom/cymrite.pdf Handbook of Mineralogy]. Accessed October 15, 2010.
3. (May 2022). "Mineral Database | National Museum Wales".
4. [http://www.webmineral.com/data/Cymrite.shtml Webmineral data] Accessed September 5, 2010
5. [http://www.mindat.org/min-1205.html Mindat.org]. Accessed September 27, 2010
6. O'Donoghue, M. (1976) The Encyclopedia of Minerals and Gemstones. Orbis Publishing, London.
7. [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cymrite Mineralienatlas]

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