Elemental (Evolution) Stones are the stones used to evolve certain Pokémobs. Some examples are listed below.
All stones can be bought from merchants in Pokecenters, some are dropped by Pokémobs, and most can be crafted.
To use a stone, just select it and right click the pokémob.
The Leaf Stone can be used to evolve Eevee to Leafeon.
The Shiny Stone can be used to evolve Minccino into Cinccino.
The Dusk Stone can be used to evolve Misdreavus into Mismagius
The Dawn Stone can be used to evolve a male Kirlia into Gallade.
The Moon Stone can be used to evolve Clefairy into Clefable.
The Sun Stone can be used to evolve Sunkern into Sunflora.
Packed Ice (Ice Stone)
Currently there are no Ice Stones in the game so Pokémobs that use Ice Stones to evolve use Packed Ice instead. Alolan Vulpix uses it to evolve into Alolan Ninetales, and Alolan Sandshrew to Alolan Sandslash.
Not an evolution stone. Prevents evolution if held.