Quarb crystal

Quarb crystals were used in the building of Hellstorm Firebell engines. When a tour bus crashed into a satellite the crystal was broken. The Doctor had a replacement in his TARDIS, declaring it the only one this side of the Softel Nebula, he gave it to Murray who accidently broke it. The Doctor grew a new one in 24 hours by accelerating the growth through use of the TARDIS' thermo-booster. (DW: Delta and the Bannermen)