Vivianite
Species
Uncommon · Fe₃(PO₄)₂·8H₂O
Iron phosphate hydrate that forms colourless when fresh but rapidly turns blue-green upon oxidation of ferrous to ferric iron. Found encrusting fossils in clay deposits. Crystals darken progressively with exposure to light.
Identity
- Formula
- Fe₃(PO₄)₂·8H₂O
- Chemical class
- Phosphate
- Also known as
- Blue ocher (earthy form)
Crystallography
- Crystal system
- Monoclinic
- Habits
- Prismatic, Massive, Earthy
- Fracture
- Fibrous
Physical properties
- Mohs hardness
- 1.5
- Density
- 2.68 g/cm³
- Luster
- Vitreous, Pearly
- Colors
- blue, blue-green, green, colorless (fresh)
- Streak
- white, altering to dark blue or brown
- Transparency
- Transparent, Translucent
Geology
- Origins
- Sedimentary, Hydrothermal
- Host rocks
- Sandstone, shale and clay
- Associated minerals
- Pyrite, Pyrrhotite, ludlamite, metavivianite
- Found in
- Bog iron
- Geography
- Bolivia, Germany, USA, Russia, Cameroon
Classification
- Rarity
- Uncommon
- Gem quality
- No
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Vivianite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
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