Pigments—Iron-based red, yellow, and brown ochres.

Natural Fe-bearing ochres ranging in color from yellow to deep red and brown abound on earth’s crust. Quite often, ochres can be used for pigmenting purposes upon little or no processing, and, hence, the pertinent materials have been widely employed for decorative and artistic purposes since the dawn of prehistory; ochres have also found medicinal applications. This paper offers an overview regarding the range and composition of the available natural ochre pigments, their origin, properties, and potential processing. In addition, the production and processing of artificial ochres is presented. The prevailing analytical techniques currently employed in ochres’ identification and provenancing are also discussed, and guidelines for good practice are provided. Finally, authors offer some insight on ochres’ potential applications and their limitations, while a discussion pertaining to ochres in the Greco-Roman world is also included. [ABSTRACT FROM AUTHOR]