they are not made of light foo
These Adegan crystals are ideal for the creation of lightsabers, as they focus the energy released from a saber's power cell into the tight, blade-like beam. Early lightsabers did not have self-contained power cells, and were instead connected by a conducting cable to a belt-worn power pack.
Once unleashed, the power channels through a positively charged continuous energy lens at the center of the handle. The beam then arcs circumferentially back to a negatively charged high energy flux aperture. A superconductor transfers the power from the flux aperture to the power cell. As a result, a lightsaber only expends power when its blade cuts through something. So efficient is the blade, that it does not radiate heat unless it comes into contact with something.
The blade's color depends on the nature of the jewel it springs from, and while its length is fixed in the case of a single-jewel lightsaber, lightsabers equipped with multiple crystals can have their length varied by rotating a knob that allows the focusing crystal activator to subtly modify the refraction pattern between the gems.