In the paper we show C*’, as described above—compaction ➡️ dilation. We also demonstrate the opposite process—dilation to compaction, which we refer to as C’* (C prime star). As far as we know, we are the first to show this formally through experiments. But wait, there’s more!

There should theoretically exist a zone in porosity–stress space where a rock can *repeatedly* switch deformation style. And lo–one of our samples exemplifies this quirky behaviour. First it compacts, then dilates, then compacts, then dilates, then compacts, then dilates…