Messelite
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Messelite is a mineral with formula Ca2(Fe2+,Mn2+)(PO4)2·2H2O. It was discovered in Germany and described in 1890. The mineral was subsequently discredited in 1940, reinstated and named neomesselite in 1955, and the name restored to messelite in 1959.
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Messelite | |
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General | |
Category | Phosphate mineral |
Formula (repeating unit) | Ca2(Fe2+,Mn2+)(PO4)2·2H2O |
IMA symbol | Msl[1] |
Strunz classification | 8.CG.05 |
Dana classification | 40.2.2.2 |
Crystal system | Triclinic |
Crystal class | Pinacoidal (1) (same H-M symbol) |
Space group | P1[2] |
Unit cell | a = 5.8 Å, b = 6.6 Å, c = 5.5 Å α = 102°, β = 109°, γ = 90°; Z = 1 |
Identification | |
Color | White, pale greenish white, greenish gray, pink,[2] colorless[3] |
Cleavage | Perfect on {001}, producing curved irregular surfaces[2] |
Fracture | Uneven[3] |
Mohs scale hardness | 3.5 |
Diaphaneity | Translucent[2] |
Specific gravity | 3.16[2] |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.644 nβ = 1.653 nγ = 1.680 |
Birefringence | δ = 0.036 |
2V angle | 20° to 35° (measured) |
Dispersion | Relatively strong |
References | [4] |
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