Metavivianite

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
Category Phosphate mineral
Formula
(repeating unit)		 Fe3+
2(PO
4)
2(OH)
2·6H
2O
Strunz classification 8.DC.25 (10 ed)
7/C.14-20 (8 ed)
Dana classification 40.11.9.4
Crystal system Triclinic
Crystal class Pinacoidal (1)
Space group P1
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)°
Identification
Formula mass 443.734 g/mol
Color Dark blue to blue-black; Dark green to green-black
Crystal habit Bladed crystals, often with irregular acute multiple terminations.
Twinning {110}
Cleavage Perfect on {110}
Tenacity Sectile
Mohs scale hardness 1.5-2
Luster Sub-vitreous, Resinous, Greasy, Dull
Streak Blue or greenish blue
Diaphaneity translucent
Specific gravity 2.69
Optical properties Biaxial (+)
Refractive index nα = 1.600 - 3.000, nβ = 1.640 - 3.000, nγ = 1.685 - 3.000[1]
Birefringence δ = 0.050 - 0.085
Pleochroism Visible; X = blue to blue-green; Y,Z = yellow-green
2V angle Measured: 85° (5), Calculated: 90°
Dispersion Very weak
Ultraviolet fluorescence Not fluorescent
References [1][2][3]

Metavivianite (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 and dehydrated vivianite.[1] 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.[2]

See also

References

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


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