Its body has been compressed deep under the ground. As a result, it is even harder than a diamond.
Silver
It is said that if an ONIX lives for over 100 years, its composition changes to become diamond-like.
Crystal
The many small metal particles that cover this POKéMON's body reflect bright light well.
Ruby
STEELIX lives even further underground than ONIX. This POKéMON is known to dig towards the earth's core. There are records of this POKéMON reaching a depth of over six-tenths of a mile underground.
Sapphire
Emerald
STEELIX live even further underground than ONIX. This POKéMON is known to dig toward the earth's core, reaching a depth of over six-tenths of a mile underground.
FireRed
It is said that if an ONIX lives for over 100 years, its composition changes to become diamond-like.
LeafGreen
Its body has been compressed deep under the ground. As a result, it is even harder than a diamond.
Diamond
Tempered underground under high pressure and heat, its body is harder than any metal.
Pearl
It chews its way through boulders with its sturdy jaws. Its eyes can see in the darkness underground.
Stadium 2
Its body has been compressed deep under the ground. As a result, it is even harder than a diamond.
TCG
Shining Steelix: If an Onix lives 100 years or more, its skin hardens, eventually becoming even harder than a diamond.