Ochre n. : A impure earthy ore of iron or a ferruginous clay, usually red (hematite) or yellow (limonite), -- used as a pigment in making paints, etc. The name is also applied to clays of other colors.

Ochre n. : A metallic oxide occurring in earthy form; as, tungstic ocher or tungstite.

Ochre n. : See Ocher.

Example:
What is your opinion of synthetic Iron Oxide and natural Iron Oxide that are used in Ochre oil paints?

Taxonomy
ochre, red ochre, pigment, Yellow ochre, paint, hues, Clay earth pigment, Iron oxide pigments, free encyclopedia, Ochres, ground, the ancient Mediterranean, Archaeology, Red ocher, seal oil, oil paint, Purple, South Africa.

Defination from the web:
ochre, or Goethite ... The remaining ochre is then dried in the sun and sometimes burned to enhance the natural color. As a painting pigment, it exists in at ... Brown ochre (Goethite), also partly hydrated iron oxide (rust) They are found throughout the world in many shades. ...