Printstone

A local marketing name for a siliceous siltstone with a distinctive iron oxide-based graphic pattern found near Tom Price, Pilbara Region, Western Australia, Australia. Some think that this material was at one time stromatolites, due to some local concentric banding, but the irregular nature of the banding shows that it's not. The ferruginous pattern is the result of Liesegang Banding, due to fluid flow, and it is closely related to Zebra stone (Zebra Rock).

A detailed study by Coward et al. (2025) showed that the printstone "patterns probably arose from the periodic deposition of hydrothermal pyrite during the early Palaeoproterozoic, as evidenced by the distinctive cuboid morphology of the hematite pigment, the deposition of iron oxides along fluid-transport pathways, the presence of extensive hydrothermal pyrite elsewhere in the formation, and the presence of a positive europium anomaly. Through spatial analysis of the iron-oxide banding, we further show that print stone adheres to the Liesegang spacing law with a spacing coefficient of 0.018. This suggests that the periodic deposition of pyrite in print stone arose due to the Liesegang phenomenon, which was probably triggered by the infiltration of near-neutral, sulfidic hydrothermal fluids into a ferruginous, feldspathic shale".