Kryptonite gem
Kryptonite is a gem that is added with the Superheroes Unlimited mod and can only be gained by mining Kryptonite ore
Mining
Kryptonite can be found in the lower levels of the minecraft world and can only be mined by a iron diamond or Kryptonite pickaxe
Use
Kryptonite can be used to make Kryptonite pickaxe and Kryptonite swords which are on par with diamond equipment though instead of sticks they use iron