The garnet- and/or clinopyroxene-bearing amphibolite mass 0.2×1.1km² in size occur being surrounded partly by serpentinite of the Kurosegawa Tectonic Zone near Kochi City.
The Mg-Fe²⁺ partitioning coefficient between coexisting garnet and clinopyroxene indicates that the amphibolite was formed under the granulite facies condition of metamorphism.
Pargasitic hornblende which is a major constitutent of the rock, was separated to provide for dating. It gave K-Ar age of 409±21 Ma, which corresponds to that of the so-called Terano metamorphic rocks, suggesting that it may be grouped as one of the members of the Terano metamorphic rocks.