Metavivianite (Fe2+
Fe3+
2(PO
4)
2(OH)
2·6H
2O) is a hydrated iron phosphate mineral found in a number of geological environments. As a secondary mineral it is typically formed from oxidizing vivianite.[2] Metavivianite is typically found as dark blue or dark green prismatic to flattened crystals.
Quick Facts General, Category ...
| Metavivianite |
|---|
 A 6x4 cm specimen of paramorphosed olive-green to green Metavivianite after oxidized vivianite. From Kerchenskoe deposit, Crimea Oblast, Ukraine. Photo and collection specimen by Pavel Kartashov. |
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| Category | Phosphate mineral |
|---|
| Formula | Fe2+
Fe3+
2(PO
4)
2(OH)
2·6H
2O |
|---|
| IMA symbol | Mviv[1] |
|---|
| Strunz classification | 8.DC.25 (10 ed)
7/C.14-20 (8 ed) |
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| Dana classification | 40.11.9.4 |
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| Crystal system | Triclinic |
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| Crystal class | Pinacoidal (1) |
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| Space group | P1bar |
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| Unit cell | a = 7.989(1) Å, b = 9.321(2) Å
c = 4.629(1) Å; α = 97.34(1)°; β = 95.96(1)°; γ = 108.59(2)° |
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|
| Formula mass | 499.548 g/mol |
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| Color | Dark blue to blue-black; Dark green to green-black |
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| Crystal habit | Bladed crystals, often with irregular acute multiple terminations. |
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| Twinning | {110} |
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| Cleavage | Perfect on {110} |
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| Tenacity | Sectile |
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| Mohs scale hardness | 1.5–2 |
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| Luster | Sub-vitreous, Resinous, Greasy, Dull |
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| Streak | Blue or greenish blue |
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| Diaphaneity | translucent |
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| Specific gravity | 2.69 |
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| Optical properties | Biaxial (+) |
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| Refractive index | nα = 1.600 – 3.000, nβ = 1.640 – 3.000, nγ = 1.685 – 3.000[2] |
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| Birefringence | δ = 0.050 – 0.085 |
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| Pleochroism | Visible; X = blue to blue-green; Y,Z = yellow-green |
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| 2V angle | Measured: 85° (5), Calculated: 90° |
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| Dispersion | Very weak |
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| Ultraviolet fluorescence | Not fluorescent |
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| References | [2][3][4] |
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It was named by C. Ritz, Eric J. Essene, and Donald R. Peacor in 1974 for its structural relationship to vivianite.[3]
