In our contest over the years, there have been some pretty amazing crystals grown.

However nothing to match this one being measured by researcher Ruth Hawley-Fedder. This 315 kg whopper of potassium dihydrogen phosphate was grown in a record 52 days at the Lawrence Livermore National Laboratory in California.

The process began with a machined potassium dihydrogen phosphate seed crystal, put in a tank almost two metres tall, filled with a tonne of super-saturated solution maintained at 70°C. The temperature was then gradually decreased to maintain supersaturation as the crystal removed salt from the solution.

"We could have grown it even larger," Hawley-Fedder said, "but we ran out of room in the tank."

This crystal will be used in the construction of a giant laser.