Luke has two lightsabers throughout the original trilogy. The original one that was Anakin's obviously had an Ilum Crystal, being that it was crafted while he was a Jedi.
But when that saber gets lost somehow, he's forced to craft a new one. Since the Empire had a blockade on Ilum, and Luke's new saber makes a much different noise when ignited, I'm thinking it's got a different type of crystal. The question is, if we had to assign one of the crystal types given in the book, which one would make the most sense?
He does hail from Tatooine, so there's a possibility that it's a Krayt Dragon Pearl, but I'm not sure if the sound it makes qualifies as a "howling" sound.
If we want to be cheesy, we could say it's a Rubat stone from the GM Kit's adventure (which is statistically identical to an Ilum crystal), but I'm not sure.
So, what do people think?