Disambiguation
"Crystal Focus"
There is no item called "Crystal Focus" in OSRS. You are likely confusing two different things.
Did you mean?
Teleport Focus
Used for ship teleportation.
Crystal Extractor
Used for resource harvesting.
1. Teleport Focus
If you are looking for the facility that allows you to teleport your ship to different ports, you mean the Teleport Focus.
It is built in a Medium Slot on your ship.
Read the Teleport Focus Guide →2. Crystal Extractor
If you are looking for the Crystal item that goes on your ship, you mean the Crystal Extractor.
Read the Crystal Extractor Guide →