Where to find Onix in Diamond, Pearl & Platinum

Walk: Sinnoh Victory Road (40%), Iron Island (30%, Swarm), Oreburgh Mine (20%) + 3 more

Iron Island (1F, B1F Left Room, B1F Right Room, B2F Left Room, B2F Right Room, B3F) — Walk
Oreburgh Mine (B1F, B2F) — Walk
Snowpoint Temple (1F, B1F, B2F, B3F) — Walk
Stark Mountain — Walk
Victory Road (1F, 1F (Room 1), 1F (Room 3), 2F, B1F) — Walk
Wayward Cave (1F, B1F) — Walk