In the series, the most essential and valuable commodity in the universe is melange, a drug that gives the user a longer life span, greater vitality, and heightened awareness.

Melange is a drug that prolongs life and bestows heightened vitality and awareness, and in some humans unlocks prescience, a form of precognition based in genetics but made possible by use of the spice.

[2][3] In larger quantities, the spice possesses intense psychotropic effects and is used as a powerful entheogen by both the Bene Gesserit and the Fremen people of Arrakis to initiate clairvoyant and precognitive trances, access genetic memory, and heighten other abilities.

"[4] Jon Michaud of The New Yorker wrote: "Imagine a substance with the combined worldwide value of cocaine and petroleum and you will have some idea of the power of melange.

"[6] Extensive use of the drug tints the sclera, cornea, and iris of the user to a dark shade of blue, called "blue-in-blue" or "the Eyes of Ibad",[7] which is something of a source of pride among the Fremen and a symbol of their tribal bond.

The man had lost one of his masking contact lenses, and the eye stared out a total blue so dark as to be almost black.Melange is also highly addictive,[10] and withdrawal means certain death.

In the first chapter of Dune Messiah, Guild Navigator Edric is described in his tank of spice gas as "an elongated figure, vaguely humanoid with finned feet and hugely fanned membranous hands—a fish in a strange sea.

[11] Herbert also indicates fluorescence in God Emperor of Dune (1981) when the character Moneo notes: "Great bins of melange lay all around in a gigantic room cut from native rock and illuminated by glowglobes ...

[11] Herbert notes in Dune that a pre-spice mass is "the stage of fungusoid wild growth achieved when water is flooded into the excretions of Little Makers",[14] the "half-plant–half-animal deep-sand vector of the Arrakis sandworm".

A gigantic bubble of carbon dioxide was forming deep in the sand, heaving upward in an enormous "blow" with a dust whirlpool at its center.

[6] Collecting the melange is hazardous in the extreme, since rhythmic activity on the desert surface of Arrakis attracts the worms, which can be up to 400 meters (1,300 feet) in length and are capable of swallowing a mining crawler whole.

In the Prelude to Dune prequel trilogy by Brian Herbert and Kevin J. Anderson (1999–2001), Project Amal is an early attempt by the Bene Tleilax to create synthetic melange in order to eliminate dependence upon Arrakis.

[16] Although Tleilaxu Master Hidar Fen Ajidica manages to create an artificial melange (called "ajidamal", or "amal") that seems to have the original's properties, it does not work properly.

When Duke Leto Atreides invades Xuttuh in 10,175 A.G. and reestablishes Prince Rhombur of House Vernius as ruler of Ix, all the records of Project Amal are destroyed by Fenring.

Sure to die should they be without the spice, a group of Navigators commission Waff, an imperfectly awakened Tleilaxu ghola, to create "advanced" sandworms able to produce the melange they so desperately require.

This new form of spice is so powerful that a relatively small dose causes a potential Kwisatz Haderach to descend into a complete and unbreakable coma through perfect prescience.

[17] In Mycelium Running, mycologist Paul Stamets argues without sources, that Herbert's creation of melange was related in part to his own personal experiences with psilocybin mushrooms.