Wöhlerite
| Wöhlerite | |
|---|---|
| General | |
| Category | Minerals |
| Formula | NaCa2(Zr,Nb)(Si2O7)(O,OH,F)2 |
| IMA symbol | Wöh |
| Strunz classification | 9.BE.17 |
| Dana classification | 56.2.4.5 |
| Crystal system | Monoclinic |
| Crystal class | H-M Symbol: 2 Sphenoidal |
| Space group | P21 |
| Unit cell | 764.21 |
| Identification | |
| Color | Honey yellow, wine yellow to sulfur yellow, light to dark yellow, brown, gray |
| Twinning | Twin planes common on {010} |
| Cleavage | Distinct on {010} Poor on {100}, {110} |
| Fracture | Irregular, uneven, splintery |
| Tenacity | Brittle |
| Mohs scale hardness | 5.5 – 6 |
| Luster | Vitreous |
| Streak | Pale yellow |
| Diaphaneity | Transparent, translucent |
| Specific gravity | 3.40 – 3.44 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.700 – 1.705 nβ = 1.716 – 1.720 nγ = 1.726 – 1.728 |
| Birefringence | 0.026 |
| Pleochroism | Weak |
| 2V angle | Measured: 70°–77° Calculated: 70° to 76° |
| Dispersion | Weak r > v |
| Ultraviolet fluorescence | None |
Wöhlerite, also known as woehlerite or wohlerite, is a member of the Wöhlerite group. It was named after German chemist Friedrich Wöhler. It was first described by Scheerer in 1843, but the crystal structure was only solved by Mellino & Merlino in 1979. Once approved, it was grandfathered by the IMA.