Ochre: the Substance

Image: Chip Clark, Human Origins Program, Smithsonian Institution

Image: F. d'Errico, R. Garcia Moreno, R.F. Rifkin

These two images are of pieces of red ochre from South Africa. The first photograph shows a model of a 70,000 years old block of ochre from the Blombos Cave. The second photograph is of a fragment of ochre from the Klasies River Cave. The fragment is 100,000 years old. The first block is clearly marked with the symbol for ochre. The second piece also had a design or symbol of some kind. I think that it may have been a similar symbol. If I am correct, it means that humans were using symbols to communicate, at least 100,000 years ago.

So why is the design on the block from the Blombos Cave the symbol for ochre, or more precisely the symbol for red ochre? To understand, you need to look at the picture of ochre on the right. It is a resonant tunneling model image of hematite; iron(III) oxide (Fe₂O₃), taken at 500 m V.

Image: Carrick M Eggleston et al.: Annotation: Lynn Fawcett

By adding lines to the image, we get a symbol that is based on the molecular structure of hematite.

Then, in the image below, you can see the symbol compared to the block of red ochre from the Blombos Cave.

Image: Chip Clark, Human Origins Program, Smithsonian Institution: Annotation: Lynn Fawcett

Author's Note

Christopher Henshilwood et al. have analysed the engraving on the block of red ochre from the Blombos Cave¹. The engraving was made in four stages. Diagonal lines sloping from lower left to upper right in relation to the photographs above were created first. Then diagonal lines sloping from lower right to upper left were added. Next the diagram was adjusted by adding two more lines going from lower left to upper right. Lastly, the horizontal lines were created. My interpretation is that the form of the symbol is intentional.

The engraving on the piece of ochre from Klasies River was analysed by Francesco d’Enrico et al.². In this example, the cross-hatched image on the right of the piece is derived from a mixture of pre-existing striations, and engraved lines. Therefore, the link with the symbol for ochre is tenuous. Did the artist intentionally borrow the form of the striations, or is it a mere coincidence?

Now, let's look at how cross-hatching was used to denote the colour ochre.

References

Image Credits:

Model of a piece of ochre from the Blombos Cave: Chip Clark, Human Origins Program, Smithsonian Institution: National Museum of Natural History: http://humanorigins.si.edu/evidence/behavior/blombos-ocher-plaque: Accessed: 6 December 2011

Close-up view of an engraved ochre fragment from the Klasies River Cave 1: Francesco d’Errico, Renata García Moreno, Riaan F. Rifkin: Technological, elemental and colorimetric analysis of an engraved ochre fragmentfrom the Middle Stone Age levels of Klasies River Cave 1, South Africa: Fig. 5., p. 947 Close-up view of the engraved area (top) and tracing of the engraved lines (bottom) on KRM 13: Journal of Archaeological Science Volume 39, 2012, pp. 942-952

RTM Image: Carrick M Eggleston, Andrew G Stack, Kevin M Rosso and Angela M Bice: Adatom Fe(III) on the hematite surface: Observation of a key reactive surface species: Figure 9: Geochemical Transactions, 2004: http://www.geochemicaltransactions.com/content/5/2/33: Accessed: 12 April 2012

Notes:

1. Christopher S. Henshilwood, Francesco d’Errico, Ian Watts: Engraved ochres from the Middle Stone Age levels at Blombos Cave, South Africa: Figure 10. Order of the engravings on piece M1-6: Journal of Human Evolution Volume 57, 2009, p. 35: Source: http://www.academia.edu/6042891/Engraved_ochres_from_the_Middle_Stone_Age_levels_ at_Blombos_Cave_South_Africa: Accessed: 6 October 2014

2. Francesco d’Errico, Renata García Moreno, Riaan F. Rifkin: Technological, elemental and colorimetric analysis of an engraved ochre fragment from the Middle Stone Age levels of Klasies River Cave 1, South Africa: Journal of Archaeological Science Volume 39, 2012, pp. 942-952