Chemistry:Cymrite
| Cymrite | |
|---|---|
 Cymrite (2.2 x 1.6 x 1.6 cm) | |
| General | |
| Category | Phyllosilicate |
| Formula (repeating unit) | BaAl2Si2(O,OH)8·(H2O) |
| 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 |
| |re|er}} | 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 | [1][2][3][4][5][6] |
Cymrite is a silicate mineral with the chemical formula BaAl2Si2(O,OH)8·H2O.[4] The mineral is named for Cymru, which is the Welsh word for Wales.[3]
Cymrite, with perfect cleavage and a monoclinic crystalline system, falls in the silicate group.[4] Silicates are formed of Silicon and Oxygen bonding together to form tetrahedra.[5] 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.[4] 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.[1] 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
- ↑ 1.0 1.1 Handbook of Mineralogy. Accessed October 15, 2010.
- ↑ "Error: no
|title=specified when using {{Cite web}}". http://www.museumwales.ac.uk/en/mineralogy/database/?mineral=209. - ↑ 3.0 3.1 Webmineral data Accessed September 5, 2010
- ↑ 4.0 4.1 4.2 4.3 Mindat.org. Accessed September 27, 2010
- ↑ 5.0 5.1 [O'Donoghue,M. (1976) The Encyclopedia of Minerals and Gemstones. Orbis Publishing, London].
- ↑ Mineralienatlas
- ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.
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