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Vivianite Mineral Facts:

Chemical Formula: Fe₃(PO₄)₂ -8(H₂O)

Colors: The fresh, pure mineral is colorless and transparent, but specimens usually seen are more or less oxidized and have a blue or green color. Its streak is white or bluish, changing to indigo-blue or brown on exposure to the air.

Hardness: 1.5 to 2.0

Density: 2.6

Cleavage: Perfect, pinacoidal cleavage.

Crystallography: Monoclinic, prismatic crystals

Luster:. Vitreous to pearly luster.  Transparent when fresh to opaque on exposure.

Optics: (Refractive Index):  a=1.5818, b=1.6012, y=1.6360.

Composition, Structure and Associated Minerals:
A rare mineral of secondary origin, associated with pyrrhotite, pyrite, limonite and other iron minerals. It has a very high water of crystallization content. Its pleochroism is strong in blue and pale yellow tints. When viewed parallel to the vertical axis, it usually appears blue, while at right angles to the vertical axis it looks green.

Identification and Diagnostics
The mineral is easily recognized by its softness, easy fusibility and by yielding the test for phosphorus. In the closed tube vivianite whitens, exfoliates and yields water at a low temperature. It fuses easily (2), tingeing the flame bluish green. Its fused mass forms a grayish black magnetic globule. It gives the reaction for iron, and is soluble in HCl.

Occurrence, Localities and Origins:
Vivianite is a secondary mineral that sometimes occurs in veins of copper, tin and gold ores; It also occurs disseminated through peat, clay, and and especially with bog iron ore. It occurs with limonite; coating the walls of clefts in feldspars and other minerals of certain igneous rocks, and partially filling cavities in fossils and partly fossilized bones. It is usually the result of the decomposition of other minerals which contain iron and phosphate.

Crystals are found at several points in Cornwall, England; in the gold mines at Verespatak, in Romania; Bodenmais in Bavaria, at Allentown, Monmouth County, New Jersey, and at many other places. The earthy variety occurs at Allentown, Mullica Hill and other points in New Jersey, in Stafford County, Virginia, and in swamp deposits at many places. It is abundant in limonite at Vaudreuil, in Quebec, and in bog iron ores elsewhere.

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