Quarb crystal

Quarb crystals were used in the construction of Hellstorm Fireball engines.

A Nostalgia Tours space cruiser used a Hellstorm Fireball. It crashed into a satellite and the crystal was broken. The Seventh Doctor had a replacement in his TARDIS, declaring it the only one this side of the Softel Nebula, he gave it to Murray who accidentally broke it. The Doctor grew a new one in 24 hours by accelerating the growth through use of the TARDIS' thermo-booster. (TV: Delta and the Bannermen)