Ochre is one of a variety of forms of iron oxide which are described as
These pigments, used by ancient and modern artists, are made of iron
oxyhydroxide, which is to say they are natural minerals and compounds
composed of varying proportions of iron (Fe3 or Fe2), oxygen (O) and
Other natural forms of earth pigments related to ochre include sienna,
which is similar to yellow ochre but warmer in color and more translucent;
and umber, which has goethite as its primary component and incorporates
various levels of manganese.
Red oxides or red ochres are hematite-rich forms of yellow ochres,
commonly formed from aerobic natural weathering of iron-bearing minerals.
Prehistoric and Historic Uses Natural iron-rich oxides provided
red-yellow-brown paints and dyes for a wide range of prehistoric uses,
including but in no way limited to rock art paintings, pottery, wall
paintings and cave art, and human tattoos.
Ochre is the earliest known pigment used by humans to paint our
world--perhaps as long ago as 300,000 years. Other documented or implied
uses are as medicines, as a preservative agent for animal hide
preparation, and as a loading agent for adhesives (called mastics).