Fig. 6: Rb/Sr–K₂O/CaO diagrams showing distinct geochemical fields for the three gabbroic stones used in early 20th-century Japanese architecture.

The plots of the three gabbroic stones, Ukigane, Nakoso, and Matsuba, are clearly separated based on pXRF values plotted before (left) and after (right) adjustment using WD-XRF bulk compositions, demonstrating distinct geochemical fields for each. The result indicates that the adjustment has minimal effect on stone discrimination.