Abstract A fragmentarily preserved Byzantine icon made of steatite was discovered in 2015 during regular excavations in Chełm, eastern Poland. Identified as the left wing of a diptych illustrating the Twelve Great Feasts and created at the close of the 12th century, the find is one of the most important and beautiful Byzantine artefacts to have been found in Poland. The icon was uncovered within the confines of the palace complex which was created by Daniel (Danylo) Romanovych († 1264) in Chełm in the second quarter of 13th century. The icon, even though it was found within the borders of what is now Poland, is material evidence of contact between Byzantium and the social elite of the Galicia-Volhynia lands, rather than with the Polish Piasts. In this paper we concentrated on the presentation of the archaeological context of the find, which made it possible to establish that the icon arrived Chełm before the middle of the 13th century (terminus ante quem 1253), and especially on petrographic and traceological analyses of the icon. Assuming that greenish plaques were indeed the most characteristic steatite icon type, a decision was made to examine, apart from the Chełm artefact made from white rock, a greenish icon from the National Museum in Krakow as well. Petrographic analyses were based on optical microscopy, scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) and X-ray powder diffraction (XRPD). Both icons were carved in steatite i. e. talc rich rock but their chemical compositions indicate the presence of other components. Artifact from Chełm is white. Porous, enriched in potassium (K) and locally blistering outer rim of the icon from Chełm was formed probably during the fire event. Presence of forsterite and subordinate amount of leucite also indicate high temperature influence. Local enrichment in calcium (Ca) is related to exchange reactions with ground compounds. Accumulation of different components on the surface of the icon’s surface was noted. The icon from the National Museum in Krakow is greenish probably because of the presence of chlorite. The results of the traceological analysis (icon from National Museum in Krakow was not analysed) indicate that the icon found in Chełm was created most likely by a skilled and experienced carver with access to the high-quality magnifying glass and specialist tools required for rendering minuscule objects and their details. The production of the icon also involved the use of a “mechanical” tool, probably a kind of a miller with a rotating polishing head, which also seems to point to a specialist workshop. The use-wear traces observed on artefact are limited to polish resulting from prolonged contact with human hands or storing the icon in a leather case. Most of the extant Byzantine icons are unprovenanced objects held in museum collections or church treasuries. Therefore, as the icon presented in this paper was discovered during archaeological excavations, it ranks among the few Byzantine artefacts to have been found outside of this realm. The petrographic and traceological analyses conducted are the first published natural science contributions to the study of Byzantine steatite icons and we hope they will provide the impetus for undertaking such research on other Byzantine finds, helping to develop Byzantine archaeology further.