The Sapphire is an item that is needed within
Pokemon FireRed in order to fix
Celio's Machine on
One Island during the
Post Game Story. This machine will allow players to ultimately
Trade with those playing
Pokemon Emerald via the
Wireless Adapter, but it will require a player to find both the
Ruby and Sapphire before being able to do so.
Out of the two crystals, the Sapphire is much more difficult to obtain than the
Ruby. After obtaining the Ruby within
Mt. Ember on
One Island, a number of things must be done in order to obtain the Sapphire. First off, you must help Lorelie defeat
Team Rocket deep within Ice Cave on
Four Island. After doing so, you will find Team Rocket's Hideout on
Five Island. Unfortunately, you will need the second password to unlock it (having learned the first from the team Rocket Grunts back on One Island).
From there, you will need to head to
Six Island. On the southern end of Six Island is
Ruin Valley, and within it is the
Dotted Hole. This cave can only be accessed by using HM
Cut on the door, and deep within it is none other than the Sapphire. Unfortunately, immediately after finding it, a scientist working with
Team Rocket will appear and take it back to Team Rocket's Warehouse on
Five Island. As he does, he will reveal the second password to you.
With this knowledge, head back to
Five Island and infiltrate
Team Rocket's Warehouse. By defeating every Team Rocket Member within it, included the scientist that took the Sapphire from you back in the
Dotted Hole, you will obtain the Sapphire. With it in hand, return to
Celio on
One Island and give him the Sapphire. With it, you will now be able to to
Trade with those playing
Pokemon Emerald.