A scalenohedral hematite pendant (presumably a pseudomorph after a calcite crystal), excavated on Bahrain (ancient Dilmun) in the Persian Gulf from layers dated to c.1800 bc, was investigated using X-ray computed microtomography. The internal porosity was studied in 3D, showing a preferential concentration of small pores in the central part, where carbonate remnants might still be present, and larger, flattened, elongated voids in the subsurface portion. Part of the scalenohedron can be described as an intergrowth of platy hematite crystals. Microtomography also yielded data on pore-size distribution. Considerations are given to the genetic model and the provenance of the hematite pendant.