The forest across a sharp boundary between greywacke and serpentinized peridotite is described from a site with seasonal rainfall on Palawan, Philippines. The forest on greywacke was of much larger stature (trees up to 26m) than that on the serpentinized peridotite (trees up to 18m). The tree (>10cm dbh) species richness was the same on both substrata with 38 species in one 0.16ha plot on each side of the boundary. There were many more individuals in the greywacke plot (149) than on the serpentinized peridotite (114). Floristically the plots were very different, with only one tree species, an unidentified Madhuca, occurring on both sides of the boundary. The soil over the greywacke was notably more acid, had lower Mg/Ca quotients, and much lower nickel concentrations than the soil over serpentinized peridotite.