Several years ago, in the course of reconnaissance geological survey of Mionoseki district of the eastern Shimane peninsula, 20 km to the east of Matsue city, the present writer found the boulders of gneissic rocks from small cut at Shichirui area in the eastern part of this peninsula. These rocks are gneissic rocks drived from basic rocks, containing tremolite, basic plagioclase and magnetite. Judged from their lithological features, they can be correlated to the gneisses of Hida-Oki metamorphic belt. The discovery of gneissic boulders testified to the presence of mountian-land of Hida-Oki metamorphic complex in and around the present Shimane peninsula district at the dawn of the Miocene. As the occurrence of such gneissic rocks from the Shimane peninsula district seems to warrant a note from the view point of the geological genesis of green tuff regions.