Barite nodules were collected from the Singuri-bank (140m depth) on the southwest of the Oga peninsula. The largest one (diameter 22cm) was studied with optical microscope of the thin section and X-ray diffraction method. According to the results, barite nodule has been formed of core part composed of barite mineral, mantle part composed of diatom and radiolaria was alternated with barite mineral. The study of barite nodule seems to be worth while for analysis of submarine geological structure of green tuff region and development of submaine mineral resources.