Cymrite
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| Cymrite | |
|---|---|
 Cymrite (2.2 x 1.6 x 1.6 cm) | |
| General | |
| Category | Phyllosilicate minerals |
| Formula | 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.