Serandite
Serandite is a mineral with formula Na(Mn2+,Ca)2Si3O8(OH). The mineral was discovered in Guinea in 1931 and named for J. M. Sérand. Serandite is generally red, brown, black or colorless. The correct name lacks an accent.
| Serandite | |
|---|---|
Serandite from Mont Saint-Hilaire, Quebec, Canada | |
| General | |
| Category | Inosilicates |
| Formula (repeating unit) | Na(Mn2+,Ca)2Si3O8(OH) |
| IMA symbol | Srd |
| Strunz classification | 9.DG.05 |
| Dana classification | 65.2.1.5 |
| Crystal system | Triclinic |
| Crystal class | Pinacoidal (1) (same H-M symbol) |
| Space group | P1 |
| Unit cell | a = 7.683(1) Å, b = 6.889(1) Å c = 6.747(1) Å, α = 90.53(5)° β = 94.12(2)°, γ = 102.75(2)° Z = 2 |
| Identification | |
| Colour | salmon pink to orange |
| Twinning | Around [010] composition plane {100}, less commonly contact twin on {110} |
| Cleavage | Perfect on {001} and {100} |
| Fracture | Irregular, uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 5 to 5.5 |
| Luster | Vitreous to greasy; fibrous aggregates are dull to silky |
| Streak | White |
| Diaphaneity | Transparent, Translucent |
| Density | 3.34 g/cm3 (measured) |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.668 nβ = 1.671 nγ = 1.703 |
| Birefringence | δ = 0.035 |
| 2V angle | 39° |
| Dispersion | r < v moderate |
| References | |
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