Serandite | |
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![]() Serandite from Mont Saint-Hilaire, Quebec, Canada | |
General | |
Category | Inosilicates |
Formula | Na(Mn2+,Ca)2Si3O8(OH) |
IMA symbol | Srd[1] |
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[2] |
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 | [3] |
Serandite[4] 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.[5]
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