Host: Japan Association of Mineralogical Sciences
Hydrogarnet, katoite, was investigated with HP single-crystal XRD and HP and HT neutron diffraction analyses. Consequently, with the phase transformation, the space group of katoite is changed from Ia-3d to I-43d at about 5 GPa. in addition, katoite is decomposed into corundum and portlandite at 8 GPa and 900 oC.