If by Olivine you mean "olive oil", then Lots of things.
You use fly
the port in olivine city.
The Light house is at Olivine city. First use HM Fly and fly to "Olivine City". When you get there walk down to the bottom right corner of Olivine city and there's the light house.
Olivine fractures.
Its not at the port
Olivine city
go up the stairs or use the elevator
First, travel to Olivine City. Then, surf Southwest of Olivine to get to a Whirlpool. Then, use a Pokemon with Whirlpool to go across the whirlpool to get into the Whirl Islands.
strength is in olivine city in the olivine cafe
you can find olivine rocks in volcanoes in Greenland.
the cafe in olivine is to the LEFT of the poke centre,
A Fisherman gives it to you in Olivine