Quaratum was a fuel source used in Starfleet emergency thruster packs. It was generally stable but exploded when exposed to amounts of radiation around 350 rads. A standard barrel of quaratum was quite heavy and without an anti-grav unit required two adult individuals a great deal of effort to move.
The USS Enterprise-D carried several barrels of quaratum in 2368. After the ship struck a series of quantum filaments, a plasma fire ignited in cargo bay four, where the quaratum was stored. Doctor Beverly Crusher and Lieutenant Commander Geordi La Forge were trapped in the cargo bay and had to move the quaratum away from the growing plasma fire, by hand, in order to keep it from igniting. Eventually, they decided to decompress the cargo bay and blow the barrels into space. (TNG: "Disaster")