Ruby crystal

Who knew you could get so much energy from rocks?

Ruby crystals are highly coruscant gems that can be found on Earth, specifically in the ruby crystal mines of Burma. Transformers, or at least Decepticons, use them as an energy source, and claim them to be "the richest source of energy on the face of the Earth"

Fiction

Generation 1 toy bios

Laserbeak's lasers are powered by ruby crystals. Laserbeak's toy bio

The Transformers cartoon

Needing more energy to make the trip back to Cybertron and conquer it in the name of the Decepticons, Megatron ordered his troops to head to Burma and dig up ruby crystals. The amounts they found were such that Megatron believed they could power their entire home planet with them. Of course, the Autobots couldn't let this happen and blew the mines up. More than Meets the Eye, Part 2 The Decepticons still managed to get away with some concentrated energon cubes filled with ruby crystal energy. More than Meets the Eye, Part 3

Notes

In the real world, there is such a thing as a ruby laser (in fact, the first ever laser was a ruby laser), but the (synthetic) ruby serves as the means of increasing the optical power of the laser; it does not 'power' the laser in the sense of providing a power source. A misunderstanding of the ruby laser principle is presumably responsible for the presentation of ruby crystals as a power source in Transformers fiction. Laserbeak's full-length bio, as published in The Transformers Universe profile, states that the crystals 'empower' his lasers, which (given Bob Budiansky's engineering background) was probably intended to refer to the real-world amplification process. It's conceivable that George Arthur Bloom read and misunderstood this profile, and was inspired to include ruby crystals as a source of energy in More than Meets the Eye.