A “coarse-grained” metabasite body has recently been discovered within the Sambagawa metamorphic rocks in Kumakogen Town, Ehime Prefecture, Southwest Japan. The metabasite is exposed at only a few outcrops, although gravel-sized clasts from the metabasite are also found in the overlying conglomerate beds of the Eocene Hiwadatoge Formation. The metabasite rocks generally have a weak foliation compared with the well-developed foliation in the surrounding Sambagawa crystalline schists. The metabasite includes white to gray “porphyroclasts” (composed mainly of albite and zoisite) within a greenish-brown matrix (including actinolite and chlorite). Rock textures and modal mineral compositions of the metabasite gravels in the Hiwadatoge Formation are more varied than those found in outcrops of the metabasite unit itself. Mineral assemblages found in the metabasite and the surrounding mafic schist show that both rock units were metamorphosed under conditions corresponding to greenschist facies.