Vivianite – "blue earth", "blue iron swamp ore". It may turn gray if exposed to the sun for a long time.
•Chemical description: Iron phosphate. The mineral is amorphous.
•Chemical formula: Fe²⁺₃(PO₄) ₂·8H₂O
•Alkali resistance:3
•Resistance to limescale: 3
•Acid resistance:1
• Lightfastness – 5.5-6
•Suitable for Acrylic, Oil, Tempera, Watercolour/Gouache
•Dark blue color
•High covering power.