Orange ochre
Composition and Properties of Orange Ochre
The main colour-giving component of natural orange ochre (ocher) is limonite which is not a single mineral but a mixture of several iron-containing minerals among them goethite, akaganeite, lepidocrocite, and jarosite, goethite (iron oxide hydroxide α-FeOOH) being the main component.Iron oxides are stable at high temperatures but not resistant against acids. The pigment is absolutely stable as is documented by the cave paintings still in excellent condition after many thousands of years and it is also is compatible with all other pigments and is often used in mixture with several other pigments.
Names
Orange earthFrom Old French ocre (c.1300) and directly from Late Latin ocra, from Latin ochra, from Greek ochra, from ochros “pale yellow,” of unknown origin.From Online Etymology Dictionary
Preparation
The natural mineral is washed in order to separate it from sand and other impurities. The resulting sludge is dried and the pigment is ground and sieved.Deposit of natural orange ochre in Rustrel, Provence, France
History of Use
The pigment had been used since prehistoric times.Examples of use
