Obsidian (Earth-2042)

Obsidian is a material. Fortress Vader on Mustafar was an obsidian tower. When used in a lightsaber it produces a red blade. In the Covenant ceremonial Progression of the Ages, the Age of Abandonement  is represented by an obsidian stone.

Source

 * https://starwars.fandom.com/wiki/Obsidian
 * https://www.halopedia.org/Age_of_Abandonment