Mr. Mine Wiki

Blue Obsidian is the eleventh mineral you will mine. It was introduced in patch V0.25. It is used for producing income and upgrading your drill (as seen in Drill and Blueprints)

Blue Obsidian sells for $20,000 / unit and will start to occur at level 93 and achieve maximum at 399.

In the source code obsidian is called blue obsidian on occasion, however both have the exact same values.