A new method for fingerprinting ochre sources using mineral magnetic measurements

Fingerprinting of iron-rich natural pigments commonly known as ochre, provides the opportunity to trace the cultural movement of these ochres in the archaeological past. This manuscript presents a proof-of-concept approach to the analysis and characterisation of ochre deposits, through the application of magnetic analytical methods. The use of measurements such as room temperature – saturation isothermal remnant magnetisation (RT-SIRM), isothermal magnetisation sweeps (hysteresis loops) and zero-field-cooled/field-cooled (ZFC-FC) remanence allow for the identification of a magnetic mineral profile in the ochre samples, which can, in turn, be used to fingerprint sources. Using low-temperature remanence and hysteresis measurements, we have demonstrated the ability to discriminate between geological contexts and thereby contribute to the greater goal of tracing cultural exchange via the movement of ochre from their original sources. • RT-SIRM, ZFC-FC and hysteresis loops can be used to qualitatively provenance ochres. • Mixtures of hematite and goethite are used to understand the magnetic properties of natural ochres. • The study presents a proof-of-concept for the non-destructive magnetic analysis of ochre pigments.