Oku-oku Hachikuro Onsen

What it is

• A wild open-air hot spring located within a national forest in Kosaka.
• Discovered during a mineral survey in 1974 at a depth of 350 meters.
• A self-responsibility area managed as part of the Hachikuro hot spring group.
• A research site for scientists studying carbon dioxide geological storage.

What to see

• Calcium carbonate deposits that have formed a layer one meter thick.
• Carbon dioxide gas erupting directly from the hot spring source.
• Rare aragonite mineral formations created by the flowing spring water.
• Natural hot water at forty-four degrees Celsius containing iron particles.
• White mineral terraces surrounding the open-air bathing area.

Notes written by Japan Gems from facts in Japanese Wikipedia.