According to Dune, Hagal is called "the 'Jewel Planet' (II Theta Shaowei), mined out in the time of Shaddam I." In Dune it is also noted that the Golden Lion Throne of the Padishah Emperors is "carved from a single piece of Hagal quartz—blue-green translucency shot through with streaks of yellow fire."
The Prelude to Dune prequel trilogy establishes that Yvette Hagal of House Hagal is one of Emperor Elrood IX's wives, and an ancestor of Paul Atreides.
Read more about this topic: List Of Dune Planets