Metavivianite

Metavivianite (Fe3+
2
(PO
4
)
2
(OH)
2
·6H
2
O
) is a hydrated iron phosphate mineral found in a number of geological environments. As a secondary mineral it is typically formed from oxidizing and dehydrated vivianite.[1] Metavivianite is typically found as dark blue or dark green prismatic to flattened crystals.

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.
General
CategoryPhosphate mineral
Formula
(repeating unit)
Fe3+
2
(PO
4
)
2
(OH)
2
·6H
2
O
Strunz classification8.DC.25 (10 ed)
7/C.14-20 (8 ed)
Dana classification40.11.9.4
Crystal systemTriclinic
Crystal classPinacoidal (1)
Space groupP1
Unit cella = 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)°
Identification
Formula mass443.734 g/mol
ColorDark blue to blue-black; Dark green to green-black
Crystal habitBladed crystals, often with irregular acute multiple terminations.
Twinning{110}
CleavagePerfect on {110}
TenacitySectile
Mohs scale hardness1.5-2
LusterSub-vitreous, Resinous, Greasy, Dull
StreakBlue or greenish blue
Diaphaneitytranslucent
Specific gravity2.69
Optical propertiesBiaxial (+)
Refractive indexnα = 1.600 - 3.000, nβ = 1.640 - 3.000, nγ = 1.685 - 3.000[1]
Birefringenceδ = 0.050 - 0.085
PleochroismVisible; X = blue to blue-green; Y,Z = yellow-green
2V angleMeasured: 85° (5), Calculated: 90°
DispersionVery weak
Ultraviolet fluorescenceNot fluorescent
References[1][2][3]

It was named by C. Ritz, Eric J. Essene, and Donald R. Peacor in 1974 for its structural relationship to vivianite.[2]

See also

References

  1. John W. Anthony; Richard A. Bideaux; Kenneth W. Bladh & Monte C. Nichols (2005). "Handbook of Mineralogy" (PDF). Mineral Data Publishing. Cite journal requires |journal= (help)
  2. Metavivianite (Mindat.org)
  3. Metavivianite Webmineral Data


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