Go upstairs in any Pokemon center head to the lady on the far right hook up a GBA to GBA cable get a friend to do the same and trade your onix there easy.
Unfortunately, you can't get an Onix in Pokemon Emerald. To have your own Onix, you need to trade it from FireRed or LeafGreen. Hope I helped :)
you can't mate you have to trade with mario kart wii
geodude and onix
Trade Onix with a metal coat to someone eles then it will evolve thne ask for it back ,and you have a new Pokemon
i dont know if you can get a metal coat...if you get one you can trade an onix with one and get steelix
Geodude and Onix.
You must trade from FireRed or LeafGreen
Onix is uncatchable in emerald you must get one from firered or leafgreen.
Level up your Groudch
Onix can be found on seven island, six island and rock tunnel.
It evolves two pokemon: Onix and Scyther. Have each hold the Metal Coat then trade them to a friend take them back and you will get a Steelix and Scizor.
You can only get an "onix" in Pokemon sapphire if you have a Pokemon version that has an onix then use a linking cable with other GBA to trade it and then you'll have an onix but "onix's" data can't be stored in your pokedex.NOTE:You can only trade with a Pokemon version that have the same region as your Sapphire has;HOENN REGION.