They found a steel chisel and also tried to work the rock with softer chisels, and couldn't. "Analysis of an iron chisel found in Rocha do Vigio showed that Ib

They found a steel chisel and also tried to work the rock with softer chisels, and couldn't. "Analysis of an iron chisel found in Rocha do Vigio showed that Iberian stonemasons from the Final Bronze Age had the necessary tools. The researchers discovered that it consisted of heterogeneous yet astonishingly carbon-rich steel. To confirm their findings, the researchers also carried out an experiment involving a professional stonemason, a blacksmith and a bronze caster, and attempted to work the rock that the pillars were made of using chisels of different materials. The stonemason could not work the stone with either the stone or the bronze chisels, or even using an iron chisel with an untempered point."