Benamite

Benamite was a rare and unstable form of crystal which was extremely difficult to synthesize.

In 2375, the crew of the USS Voyager constructed a quantum slipstream drive, at the heart of which were benamite crystals. Although it was eventually discovered that constant phase variances in the quantum threshold could make the journey extremely hazardous, the crew elected to risk implementing the slipstream drive anyway, as the crystals had already started to decay, and synthesizing more could have taken years. 

Benomit