A metal alloy found as scrap in a Gatherer camp, which Riker vaporised with phaser fire to startle an ambush party into surrender in the episode The Vengeance Factor.
Noranium is an alloy named in The Next Generation episode The Vengeance Factor in 2366. It is not valuable in itself; the away team comes across a heap of it among the salvage and stolen goods piled up in a camp of the Gatherers, the nomadic raiders who split from Acamarian society a century earlier.
When Riker, Data, Worf and La Forge follow the trail of a raid on a Federation outpost to the camp, the Gatherers ambush them. Data observes that the scrap beside their attackers is noranium alloy and gives the temperature at which it vaporises, a little over 2,300 degrees. Riker has the team turn their phasers on the pile rather than on the Gatherers, and the sudden cloud of hot vapour drives them into the open without anyone being killed.
The encounter opens the talks through which Picard and the Acamarian sovereign Marouk try to bring the Gatherers home.