Stone Age Secrets: 48,000-Year-Old Ochre Mine Found in Eswatini

Researchers confirmed that Lion Cavern in Eswatini is the world’s oldest ochre mine, dating back 48,000 years. Using luminescence dating and geochemical methods, they traced the pigment’s origins and cultural significance, shedding light on ancient practices of extraction, use, and transport.

A recent study conducted by an international team of researchers employed luminescence dating and geochemical analyses to identify the world’s oldest ochre mine. This historic site is located in the Lion Cavern, situated in Eswatini, a country in southern Africa.

Not only have the researchers dated the mine to an age of around 48,000 years, but they were also able to show how the ochre spread from the mine to nearby areas. The researchers analysed 173 samples from 15 Stone Age sites and reconstructed the methods of ochre extraction, use and transport networks. The study was recently published in the journal Nature Communications.

Ochre is a naturally occurring pigment made from iron-rich materials. It has been used by people for thousands of years – for cave paintings and to decorate symbolic objects and personal ornaments. Ochre has cultural, historical and spiritual significance in many societies and therefore offers researchers valuable insights into the growth of human society and human self-expression.

Geochemical Fingerprinting of Ochre

For this study, the researchers created a geochemical fingerprint of the ochre from the Lion Cavern region. For this purpose, small samples of ochre artifacts are safely made radioactive by neutron irradiation. Some of the resulting products can be radioactive.

When these radioactive materials begin to decay, they emit characteristic energies. These can be measured and can thus provide information on where the material comes from and how it was created.

In this way, the origin and transport routes of the artifacts can be reconstructed. In addition to this method, the researchers used advanced laser technology, which makes the sample’s molecular bonds vibrate. This vibration indicates the mineral composition of the ochre.

Luminescence Dating: A Window into the Past

Dr Svenja Riedesel from the Cologne Luminescence Laboratory at the University of Cologne’s Institute of Geography contributed to the dating of the samples. Luminescence dating is based on the fact that materials such as quartz or feldspar absorb small amounts of energy from their surroundings over the course of time. The main source of this energy is the natural radiation in the ground, which is all around us. Small defects in the crystal structure of the material store this energy.

“To determine the age of a material, we take a sample and expose it to light or heat in the laboratory,” said Riedesel. “In this way, the stored energy is released again and a weak light – known as luminescence – is produced.” The amount of light released indicates how long the material has not been exposed to sunlight or heat.

Riedesel used quartz grains to date the materials inside of the now abandoned mining caves of Lion Cavern. The results of the luminescence samples show that the caves were created by mining at least 42,000 years ago. This confirms earlier geochronological findings suggesting that ochre was mined in the Lion Cavern 48,000 years ago. “With the help of Optically Stimulated Luminescence dating, we were able to prove that this is the oldest known ochre mine in the world,” summarized the geographer.

Reference: “Ochre communities of practice in Stone Age Eswatini” by Brandi L. MacDonald, Elizabeth C. Velliky, Bob Forrester, Svenja Riedesel, Jörg Linstädter, Alexandra L. Kuo, Stephan Woodborne, Ayanda Mabuza and Gregor D. Bader, 24 October 2024, Nature Communications.
DOI: 10.1038/s41467-024-53050-6

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