| Alleghanyite | |
| Formula: | Mn5(SiO4)2(OH)2 |
| Imasymbol: | Alh[1] |
| Molweight: | 492.87 g/mol |
| Strunz: | 9.AF.45 |
| Dana: | 52.3.2b.1 |
| System: | Monoclinic |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | P21/a |
| Unit Cell: | a = 10.46, b = 4.86 c = 8.3 [Å]; β = 109.133°; Z = 2 |
| Color: | Brown, bright pink, grayish pink, white |
| Habit: | Granular; anhedral to subhedral crystals in matrix |
| Cleavage: | None |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Mohs: | 5–6 |
| Luster: | Vitreous |
| Refractive: | nα = 1.756 nβ = 1.78 nγ = 1.792 |
| Opticalprop: | Biaxial (−) |
| Birefringence: | 0.036 |
| 2V: | 72° (meas.), 68° (calc.) |
| Gravity: | 4 (meas.), 4.11 (calc.) |
| Diaphaneity: | Transparent to translucent |
| Other: | Non-fluorescent |
| References: | [2] [3] |
Alleghanyite is a moderately rare humite mineral with formula Mn5(SiO4)2(OH)2, belonging to the nesosilicates class. In general its occurrences are related with metamorphic (metamorphosed) manganese deposits. The mineral is named after Alleghany County, North Carolina, US.[2]