Cymrite
| Cymrite | |
|---|---|
 Cymrite (2.2 x 1.6 x 1.6 cm) | |
| General | |
| Category | Phyllosilicate |
| Formula (repeating unit) | BaAl2Si2(O,OH)8·(H2O) |
| IMA symbol | Cym[1] |
| Crystal system | Monoclinic |
| Crystal class | Domatic (m) (same H-M symbol) |
| Space group | Pm |
| Unit cell | a = 5.32 Å, b = 36.6 Å, c = 7.66 Å; β = 90°; Z = 2 |
| Identification | |
| Color | Brown, greenish, colorless |
| Crystal habit | Micacious, sheet-like, pseudohexagonal, also fibrous |
| Cleavage | Perfect on {001}, good on {110} |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 2-3 |
| Luster | Silky, Vitreous |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.49 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.611 nβ = 1.619 nγ = 1.621 |
| Birefringence | δ = 0.010 |
| 2V angle | 0-5° |
| References | [2][3][4][5][6][7] |
Cymrite is a silicate mineral with the chemical formula BaAl2Si2(O,OH)8·H2O.[5] The mineral is named for Cymru, which is the Welsh word for Wales.[4]
Cymrite, with perfect cleavage and a monoclinic crystalline system, falls in the silicate group.[5] Silicates are formed of Silicon and Oxygen bonding together to form tetrahedra.[6] 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.[5] Cymrite, being monoclinic is anisotropic with two optic axes.
Occurrence
[edit]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.[2] 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
[edit]- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b Handbook of Mineralogy. Accessed October 15, 2010.
- ^ www.museumwales.ac.uk http://www.museumwales.ac.uk/en/mineralogy/database/?mineral=209. Retrieved October 2, 2010.
{{cite web}}: Missing or empty|title=(help)[title missing] - ^ a b Webmineral data Accessed September 5, 2010
- ^ a b c d Mindat.org. Accessed September 27, 2010
- ^ a b [O'Donoghue,M. (1976) The Encyclopedia of Minerals and Gemstones. Orbis Publishing, London].
- ^ Mineralienatlas