Colorful
Vivianite
Composition and Properties of Vivianite
The chemical composition of this natural pigment: hydrated iron phosphate with the formula of Fe3(PO4)2 · 8H2O. On exposure to air, the Fe2+-ions can be oxidized to Fe3+ which causes a color shift towards darker blue and blue-green.
Names
Blue ochreNamed after either John Henry Vivian, a Welsh-Cornish politician, mine owner and mineralogist living in Truro, Cornwall, England, or after Jeffrey G. Vivian, an English mineralogist.From Wikipedia
Preparation of Vivianite
The pigment is prepared from naturally occurring mineral by breaking, grounding and purifying. The whole process is shown in the video from Master Pigments below.
History of Use
It was used as a pigment since antiquity but its use in oil painting remained rare.
