How does vivianite form?

It is well known that vivianite forms as a result of oxidation–reduction reactions in sediments. Vivianite is often accompanied by an assemblage of authigenic minerals which might be precursors for vivianite, such as ferric and mixed valence Fe phases, or that form at the expense of vivianite.

What is the hardness of Vivianite?

Vivianite is a soft mineral, with Mohs hardness only 1+1⁄2 to 2, and specific gravity 2.7. It splits easily, with perfect cleavage perpendicular to the b crystal axis, due to the sheet-like structure of the mineral. It is sectile, with a fibrous fracture, and thin laminae parallel to the cleavage plane are flexible.

What are the uses of Vivianite?

Vivianite is a stone full of peace and love and will relight the care you may have lost for the closest people around you. As well as unlocking the heart, Vivianite also assists in removing negativity and unwanted energies from your mind, body, and auric field.

What is the solubility of vivianite in water?

The solubility of vivianite is given by: Fe3(PO4)2 · 8H2O ⇋ 3Fe2+ + 2 PO43− + 8 H2O and has an equilibrium constant of pK sp = 35.767 ± 0.076 at 25 °C ( Al-Borno and Tomson, 1994 ). The pH of anoxic soils and sediments is often relatively high (~ pH 7) due to the acid consuming process of iron (III) oxide reduction.

What is the general formula for the vivianite group of minerals?

Vivianite group minerals have the general formula A 3 (XO 4) 2 ·8H 2 O, where A is a divalent transition metal cation and X is either phosphorus or arsenic, and they are monoclinic. Group members are:

Is vivianite monoclinic oxidized?

Oxidation of vivianite is often reflected in a combination of the monoclinic pattern with the triclinic of metavivianite ( Rodgers and Henderson, 1986 ), but monoclinic oxidised vivianite might contain 40–50% of Fe (III), as in our soil.

How is vivianite formed?

► Vivianite is formed along pores and cracks in a gyttja layer. ► Vivianite formation via reduction of iron oxides. ► Solubility equilibrium of vivianite is slowly established (> 120 days). ► Vivianite keeps dissolved phosphate < 6 μM when pore water composition is stable. 1. Introduction