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| Metavivianite | |
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| Category: | Phosphate mineral |
| Imasymbol: | Mviv[1] |
| Molweight: | 499.548 g/mol |
| Strunz: | 8.DC.25 (10 ed) 7/C.14-20 (8 ed) |
| Dana: | 40.11.9.4 |
| System: | Triclinic |
| Class: | Pinacoidal (1) |
| Symmetry: | P1bar |
| 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)° |
| Color: | Dark blue to blue-black; Dark green to green-black |
| Habit: | Bladed crystals, often with irregular acute multiple terminations. |
| Cleavage: | Perfect on |
| Tenacity: | Sectile |
| Mohs: | 1.5–2 |
| Luster: | Sub-vitreous, Resinous, Greasy, Dull |
| Streak: | Blue or greenish blue |
| Diaphaneity: | translucent |
| Gravity: | 2.69 |
| Opticalprop: | Biaxial (+) |
| Refractive: | nα = 1.600 – 3.000, nβ = 1.640 – 3.000, nγ = 1.685 – 3.000 |
| Birefringence: | δ = 0.050 – 0.085 |
| Pleochroism: | Visible; X = blue to blue-green; Y,Z = yellow-green |
| 2V: | Measured: 85° (5), Calculated: 90° |
| Dispersion: | Very weak |
| Fluorescence: | Not fluorescent |
Metavivianite is a hydrated iron phosphate mineral found in a number of geological environments. As a secondary mineral it is typically formed from oxidizing vivianite. Metavivianite is typically found as dark blue or dark green prismatic to flattened crystals.
It was named by C. Ritz, Eric J. Essene, and Donald R. Peacor in 1974 for its structural relationship to vivianite.