Deciphering Miltos

Ancient Greek and Roman writers record the use of a substance called miltos. Miltos was red, fine-grained, and made up mostly of iron-oxide. By the time of Theophrastus, in the third century BCE, it was already a mineral validated by antiquity. The variety of applications for which it was used was broad. It was used as a pigment, as a cosmetic, in ship maintenance, agriculture and medicine. Samples were subjected to a battery of tests, including X-ray defraction, geochemical analysis, dynamic light scattering to probe nanoparticle structure, DNA sequencing to discover microbiological components, and anti-microbial tests.

Ochre is a natural clay earth pigment which is a mixture of ferric oxide and varying amounts of clay and sand.

One of the samples was found to have exceptionally high lead levels. The high lead levels mean that the powder, once mixed into an organic medium, would make an effective anti-fouling agent on ships. There are several references in Greek and Roman literature to the presence of miltos on farms and references to the use of miltos in treating disease or wounds, using it as an antibacterial agent.