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Super conductive material
Naquadah is a super-dense metallic-quartzite mineral found on many worlds in several galaxies such as the Milky Way and Pegasus. It is superconductive and capable of storing energy from many forms such as heat and electricity. The mineral is very hard and capable of withstanding a wide variety of force when in a refined state. Naquadah can also be concentrated into a liquid form and a "heavy" version of this form also exists.
The mineral is capable of amplifying the energy released in explosive technology creating a much larger explosive force. Naquadah also has an isotropic variant called Naquadria which is exponentially more powerful than Naquadah but also much more unstable when used in reactive processes such as power generation and weapons technology. (SG1: "The Torment of Tantalus", "The Fifth Race", "A Hundred Days", "Absolute Power", "Meridian")
Uses by race
The Ancients used Naquadah in the creation of the Stargates, the superconductive nature of the mineral provided a unique basis for the transportation technology. Naquadah was also incorporated into their general buildings, most likely as part of some kind of data or power transfer. They also knew of means to create a Naquadah based power source. (SG1: "The Torment of Tantalus", "Singularity", "The Fifth Race", "Fallen")
The Asgard use some Naquadah in their technology. They used a combination alloy of Naquadah, Carbon and Trinium in the construction of the first O'Neill-class spaceship, which was shortly destroyed in a battle against the Replicators. It is unknown if they use the mineral for power generation. (SG1: "Small Victories")
The Goa'uld originally had no Naquadah in their blood but over time it was incorporated into their DNA allowing them to sense the Naquadah in others as well as operate certain technology. They relied on Naquadah for almost every piece of technology using it for power generation, weapons and general technology. The Goa'uld also used a liquid-variation of Naquadah for the Staff weapons. They took control over many Naquadah rich planets and enslaved the populations to mine it for them. (SG1: "Hathor", "Seth", "The Fifth Race")
The Jaffa used much of the technology of the Goa'uld during their time as slaves and warriors and even after the defeat of their former gods much of the technology is still used by the Free Jaffa Nation. Many captured Jaffa who refused to serve their new masters were used as a slave labor to mine Naquadah on numerous planets such as Erebus as the Jaffa were the only ones able to withstand the noxious fumes and heat given off during the mining and manufactured process. (SG1: "Orpheus", "Flesh and Blood")
The Orbanians used Naquadah in the creation of Naquadah generators. It is unknown exactly how much Naquadah they had acquired, if they mined it on their own world or from another source or if they used Naquadah fro any other uses such as weapons technology. (SG1: "Learning Curve")
Naquadah was used by the Tau'ri for Naquadah generator technology and this was later incorporated into the Nuclear weapons technology to create incredibly destructive explosives. Naquadah also allowed for Earth to create interstellar spaceships by constructing hull alloys and to be used as a power source. Naquadah generators are often used to power offworld bases such as the Alpha Site and Atlantis. (SG1: "Learning Curve", "Prometheus Unbound", "Chain Reaction", ATL: "Rising")
The Tok'ra, just like the Goa'uld, have Naquadah in their blood and are able to sense other sources in other beings. The Tok'ra also use Naquadah in their technology. (SG1: "Need", "The Tok'ra, Part 1")
Behind the scenes
- The word "Naquadah" was first used in the Stargate SG-1 Season 1 episode Singularity. No explanation was given as to how or when the name of the mineral was discovered by the Tau'ri.