| OCHRE | ||
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As a painting pigment, it exists in at least four forms: * Yellow ochre, Fe2O3 • H2O, a hydrated iron oxide * Red ochre, Fe2O3, chemically identical to yellow ochre, but reddened through heating * Purple ochre, identical to red ochre chemically but of a different hue caused by different light diffraction properties associated with a greater average particle size * Brown ochre (Goethite), also partly hydrated iron oxide (rust) |
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