A special Horas Stone Block, which is highly resistant to blasts. Can be collected with Mithril Pickaxe or more advanced ones.
You can find all over the surface of Horas. This is the material for making Fluerescent Bomb, Fluorescent Ball, Ice Dart, Reflector, Horas Rock Lamina, Horas Rock Stair, Horas Rock Brick, Horas Rock Upright Lamina, Horas Rock Cantboard, Horas Rock Cantboard (Thin), Horas Rock Cantboard (Vertical/Thin), Horas Rock Riser, and Lab Door.