The Crystals are rare Ores which can be found underground in the Minecraft's world, in some new planets
underground and in special places such as secret chests.
There are many colours of them:
They are mainly used to craft the lightsabers but they could have some different utilities in the future.
Green and Red Crystals are the most common, while White and Black are the most rare (they actually can't be found in Minecraft World's underground).