The special Crystal Onix (Iwark is Japanese for Onix) is a special Onix made from glass crystal.
in the anime Ash and his freinds find a message in a bottle in the sea, they find out that the note was Written by the little girl named Marissa. She wanted to get the Crystal Onix to help her find her older brother Mateo. Mateo liked to make crystal statues of Pokemon, his grandfather ha apparently discoverd the Onix, his Grandfather also made a sculpture of it. The group manages to find the Crystal Onix, it was liveing in the lake of a large cave, it attacks and manages to knock out knock out some pokemon before Mateo uses his charmeleon wich manges to weaken the Crystal Onix, Mateo was about to capture the Onix but decided he didnt need to and has enough insperation to make it into a sculpture, he thanked the Onix the Pokemon acknowledged this and it submerged back into its underwater home.