Abstract
The Happo-O'ne ultrabasic rock mass is situated in the north-eastern part of the Hida marginal structural belt and composed mainly of dunite or serpentinized dunite.
Olivine with well-developed cleavage, which is so resemble to the “cleavable olivine” reported from northern California (Hawkes, 1946) and Komori (Kuorda and Shimoda, 1967), is discovered in the dunite of this area. The dunite containing the cleavable olivine is found in the core of the rock mass as a relict and surrounded with strongly sheared dunite. The petrographical and petrochemical characters of this rock mass are presented, and furthermore, some properties of the cleavable olivine are inspected.
