The Crystal Onix (Japanese: クリスタルのイワーク Crystal Iwark) is a rare pokemon found only on the Orange Islands (in the anime). It is made of Crystal due to eating the diamonds formed in the cave in which it lives.
It earned a name for itself, but only as a myth. The Crystal Onix appered in the anime as an inspiration for a little girl's older brother, Mateo (Ahatake), who sculpted pokemon from glass. He had lost his drive for sculpting, but he would regain it upon seeing the Crystal Onix.