Certain stones make certain Pokemon evolve.

Dawn Stone: Mt. Coronet. On the second visit the first floor.
Dusk Stone: Galactic Warehouse
Fire Stone: Fuego Ironworks. Dig underground.
Leaf Stone: Floarama Meadow. Dig underground.
Moon Stone: Occasionally Wild Clefairy and Lunatone hold it; Dig underground.
Oval Stone: Lost Tower second floor
Shiny Stone: Iron Island
Sun Stone: Solrock sometimes hold it; Dig underground.
Thunder Stone: Sunnyshore City. Dig underground.
Water Stone: Route 214. Dig underground.