Flood basalt

Basaltic flood formations existed as a form of basalt on the world of Mustafar. In the year 14 BBY, Alva Brenne, an Imperial Colonel and architect, journeyed to Mustafar with the purpose of creating a personal base for Darth Vader, the Dark Lord of the Sith. During her inspection of the fiery landscape of the planet, she discovered basaltic flood deposits near the lava flows of Mustafar, and subsequently commanded Lieutenant Roggo to perform strength assessments on the material, with the intention of potentially using it in Vader's fortress construction.