whats a ruststone and how do you get it

Someone help me that would be great

Ruststone is a type of ore you could get by killing Lao Shan, or, minning it on volcano. Then you just have to go to blacksmith to create a weapon with it. 3 type of weapon could be made in each weapon class :
- First Iron weapon (ex: iron sword, iron hammer...)
- Upgraded iron weapon (ex : knight lance, injection gun,...)
- Rust weapon.

The aim of the rust is to create the rust weapon, but you can't choose wich of 3 weapon it will be. The best way is to get at least 5rust stone for a weapon type, create the 5weapon. If you didn't get it, don't save and reset, and restart smithing.
First upgarde of weapon is jerk, but after the 3rd upgrade it starts to be cool

i only have one eternal weapon which is eternal strife