where is ruby weapon?

can someone tell me where ruby weapon is? i heard it was in the sands around golden saucer but i can only get on the sand with my gold chocobo and you dont go into battles with chocobos. how to you find him?

He's there, he appears as a red sort of... well it almost looks like a flower growing up from the sand, and yes you can get into battles on your Chocobo, if they're boss battles like that. You can also attack from your airship as well, if you fly low enough. I think.

Edit: I could be wrong about the Chocobo thing. I dont think I am, but if you cant, try dismounting when you're in the desert. The only moving parts are on the edges.

is this in the desert around golden saucer because there is another one nearby.

Its the desert around the Gold Saucer.

He only appears there once you have defeated Ultima Weapon.

Once Ultima Weapon is dead you'll see something red stickout out of the sand around the GoldSaucer. Either run into it on a Gold Chocobo or fly into it with the Highwind and the battle will start.