Understanding the Burial Environment and Post-Excavation History of Mummies

A recent study published in the Journal of Analytical Atomic Spectrometry analyzed trace metals and dust particles in black coatings and wrappings from 16 Egyptian mummies, revealing that one mummy’s bitumen originated from an unknown source rather than the commonly used Dead Sea deposits.¹ The distribution of pigments, airborne particles, and mercury residues indicates multiple historical dust exposures and suggests the mummy was treated with mercury salts in the early 19th century for preservation against biological degradation.¹

The first part of our Q&A with Didier Gourier, the study’s lead author, explored how micro-particle induced X-ray emission (µ-PIXE) and micro-ion beam induced luminescence (µ-IBIL) spectroscopy can analyze trace elements in mummy samples. In the second part of our conversation, Gourier highlights how his team learned more about the burial environment and post-excavation history of mummies using µ-PIXE and µ-IBIL spectroscopy.

The study identified distinct distributions of aluminosilicate and carbonate particles on different sides of the linen strips. What does this reveal about the burial environment and post-excavation history of the mummy?

The bitumen-coated linen strips have trapped numerous particles of very fine airborne dust present in the environment, as shown by the combination of m-PIXE and m-IBIL mapping in our study.¹ Among these mineral microparticles, the most easily identifiable are aluminosilicates, dominated by albite, and carbonates, primarily calcite. These two mineral families, which are very abundant in Egyptian geology, are not distributed uniformly across the bitumen-soaked bandage fragments. Indeed, their inner surfaces, which were pressed against the mummy, contain much more aluminosilicates than carbonates, whereas the opposite is true for the outer surfaces in contact with the environment.

These simple observations provide certain insights into the mummy’s post-mortem history. On the one hand, they show that there was an abundance of very fine airborne mineral dust in the embalming workshop, indicating that it was likely well-ventilated, which is not surprising given the need to evacuate gases emitted by a putrefying body in a hot climate. Do not forget that the entire mummy preparation process could take more than two months. Furthermore, the difference in the nature of the dust sticking to the underside of the bandages (and thus to the mummy) and to their outer surface indicates that the mineral composition of the ambient atmosphere changed between the preparation of the mummy in ancient Egypt and its excavation in the very early 19th century. The outer surface of the mummy’s bandages not only shows fewer aluminosilicates and more carbonates than the inner surface, but it also shows clusters of fine dust consisting of transition metal-rich minerals, such as rutile (TiO₂), ilmenite (FeTiO₃), and magnetite (Fe₃O₄). Such minerals are very abundant in the black sands of the Mediterranean coast of the Nile Delta, particularly between Alexandria and Port Saïd. All these observations suggest that after its excavation in southern Egypt and the opening of the coffins containing the mummy in the early 19^th century, this funerary ensemble was transported to northern Egypt, where it must have remained for some time while awaiting shipment to France.

You propose that the mummy experienced at least two separate dust exposure events. What specific spectral or spatial indicators allowed you to differentiate between these events?

To identify different dust events, it is necessary to first determine the composition of airborne mineral dust present in Egypt. Elemental analyses of this dust, based on Ca:Al ratios, allow us to estimate its origin.² It has been shown that Ca:Al values <2 correspond to dust from the Sahara transported over long distances, thus requiring strong winds to reach Egypt. Conversely, a Ca:Al ratio >6 corresponds to dust originating from chotts (or sabkhas), which are closed depressions where water accumulates temporarily and disappears rapidly, leaving a salt crust on the surface. Such saline depressions are found in the Libyan Desert north of Egypt (Qattara Depression, Siwa Oasis). Winds of low or moderate intensity are sufficient to transport this dust to the Nile Valley. Intermediate Ca:Al values between 2–6 may correspond to mixtures of the two types of dust, or to dust originating from limestone surfaces, which are abundant in Egypt.²

m-PIXE analyses of the inner surfaces of the bandage fragments, which were adhered to the mummy, are characterized by Ca/Al <2, whereas the outer surfaces show Ca:Al in the range 2 to 11. This result suggests that during the preparation of the mummy, but before the bandages were applied, dust from the Sahara was carried by a strong wind, the Khamsin. This violent wind most often blows between March and May, which gives an idea of the season in which the man was mummified. The higher Ca:Al ratios measured on the outer surfaces of the bandage fragments indicate the presence of calcite (CaCO₃) and gypsum (CaSO₄·2H₂O). It is this high Ca:Al ratio, combined with the presence of heavy minerals from the Nile Delta, that suggests that the mummy was moved from southern to northern Egypt, where it was exposed to at least one dust event prior to being shipped to Europe.

Egyptian blue pigment particles were detected in the samples. What might their presence indicate about funerary practices, workshop environments, or contamination pathways?

Among the many mineral microparticles trapped within the mummy, m-PIXE mapping revealed that many of them are copper compounds, some of which are characterized in m-IBIL mapping by a broad luminescence band in the near-infrared (NIR) region around 900 nm.These two characteristics are those of Egyptian blue, a calcium and copper silicate (CaCuSi₄O₁₀) emblematic of ancient Egypt and which was also the first synthetic pigment created by humans. Therefore, it would not be too surprising to find it on a mummy, as pigment fragments could very well have detached from the decor on the inside of the coffin and ended up in the fibers of the mummy’s bandages. However, we observed that these particles of Egyptian blue are very fine, like other airborne mineral dusts, and are trapped in the linen fibers and in the bitumen, both on the outer and inner surfaces of the strips. This indicates that they were trapped during the preparation of the mummy and therefore likely originated from the workshop environment, like other mineral dust, rather than from fragments detached from the decorative motif on the interior of the coffin.

References

1. Gourier, D.; Anduze, O.; Lemasson, Q.; et al. Tracing the Post-Mortem History of Egyptian Mummies Using Nuclear Microprobe Analysis of Trace Metal Elements and Mineral Dust Particles. J. Anal. At. Spectrom. 2026, 41, 385–403. DOI: 10.1039/D5JA00339C
2. Boraly, M.; El-Metwally, M.; Borbon, A.; et al. Elemental Ratios as Tracers of the Sources of Mineral Dust in Northeastern Sahara. Int. J. Environ. Sci. Technol. 2024, 21, 1875–1888. DOI: 10.1007/s13762-023-05077-3